Safety and immunogenicity of the Euvichol-S oral cholera vaccine for prevention of Vibrio cholerae O1 infection in Nepal: an observer-blind, active-controlled, randomised, non-inferiority, phase 3 trial

BACKGROUND

In October, 2017, WHO launched a strategy to eliminate cholera by 2030. A primary challenge in meeting this goal is the limited global supply capacity of oral cholera vaccine and the worsening of cholera outbreaks since 2021. To help address the current shortage of oral cholera vaccine, a WHO prequalified oral cholera vaccine, Euvichol-Plus was reformulated by reducing the number of components and inactivation methods. We aimed to evaluate the immunogenicity and safety of Euvichol-S (EuBiologics, Seoul, South Korea) compared with an active control vaccine, Shanchol (Sanofi Healthcare India, Telangana, India) in participants of various ages in Nepal.

METHODS

We did an observer-blind, active-controlled, randomised, non-inferiority, phase 3 trial at four hospitals in Nepal. Eligible participants were healthy individuals aged 1-40 years without a history of cholera vaccination. Individuals with a history of hypersensitivity reactions to other preventive vaccines, severe chronic disease, previous cholera vaccination, receipt of blood or blood-derived products in the past 3 months or other vaccine within 4 weeks before enrolment, and pregnant or lactating women were excluded. Participants were randomly assigned (1:1:1:1) by block randomisation (block sizes of two, four, six, or eight) to one of four groups (groups A-D); groups C and D were stratified by age (1-5, 6-17, and 18-40 years). Participants in groups A-C were assigned to receive two 1·5 mL doses of Euvichol-S (three different lots) and participants in group D were assigned to receive the active control vaccine, Shanchol. All participants and site staff (with the exception of those who prepared and administered the study vaccines) were masked to group assignment. The primary immunogenicity endpoint was non-inferiority of immunogenicity of Euvichol-S (group C) versus Shanchol (group D) at 2 weeks after the second vaccine dose, measured by the seroconversion rate, defined as the proportion of participants who had achieved seroconversion (defined as ≥four-fold increase in V cholerae O1 Inaba and Ogawa titres compared with baseline). The primary immunogenicity endpoint was assessed in the per-protocol analysis set, which included all participants who received all their planned vaccine administrations, had no important protocol deviations, and who provided blood samples for all immunogenicity assessments. The primary safety endpoint was the number of solicited adverse events, unsolicited adverse events, and serious adverse events after each vaccine dose in all ages and each age stratum, assessed in all participants who received at least one dose of the Euvichol-S or Shanchol. Non-inferiority of Euvichol-S compared with Shanchol was shown if the lower limit of the 95% CI for the difference between the seroconversion rates in Euvichol-S group C versus Shanchol group D was above the predefined non-inferiority margin of -10%. The trial was registered at ClinicalTrials.gov, NCT04760236.

FINDINGS

Between Oct 6, 2021, and Jan 19, 2022, 2529 healthy participants (1261 [49·9%] males; 1268 [50·1%] females), were randomly assigned to group A (n=330; Euvichol-S lot number ES-2002), group B (n=331; Euvichol-S ES-2003), group C (n=934; Euvichol-S ES-2004]), or group D (n=934; Shanchol). Non-inferiority of Euvichol-S versus Shanchol in seroconversion rate for both serotypes at 2 weeks after the second dose was confirmed in all ages (difference in seroconversion rate for V cholerae O1 Inaba -0·00 [95% CI -1·86 to 1·86]; for V cholerae O1 Ogawa -1·62 [-4·80 to 1·56]). Treatment-emergent adverse events were reported in 244 (9·7%) of 2529 participants in the safety analysis set, with a total of 403 events; 247 events were reported among 151 (9·5%) of 1595 Euvichol-S recipients and 156 events among 93 (10·0%) of 934 Shanchol recipients. Pyrexia was the most common adverse event in both groups (57 events among 56 [3·5%] of 1595 Euvichol-S recipients and 37 events among 35 [3·7%] of 934 Shanchol recipients). No serious adverse events were deemed to be vaccine-related.

INTERPRETATION

A two-dose regimen of Euvichol-S vaccine was non-inferior to the active control vaccine, Shanchol, in terms of seroconversion rates 2 weeks after the second dose. The simplified formulation and production requirements of the Euvichol-S vaccine have the potential to increase the supply of oral cholera vaccine and reduce the gap between the current oral cholera vaccine supply and demand.

FUNDING

The Bill & Melinda Gates Foundation.

TRANSLATION

For the Nepali translation of the abstract see Supplementary Materials section.

Incidence of typhoid fever in Burkina Faso, Democratic Republic of the Congo, Ethiopia, Ghana, Madagascar, and Nigeria (the Severe Typhoid in Africa programme): a population-based study

BACKGROUND

Typhoid Fever remains a major cause of morbidity and mortality in low-income settings. The Severe Typhoid in Africa programme was designed to address regional gaps in typhoid burden data and identify populations eligible for interventions using novel typhoid conjugate vaccines.

METHODS

A hybrid design, hospital-based prospective surveillance with population-based health-care utilisation surveys, was implemented in six countries in sub-Saharan Africa. Patients presenting with fever (≥37·5°C axillary or ≥38·0°C tympanic) or reporting fever for three consecutive days within the previous 7 days were invited to participate. Typhoid fever was ascertained by culture of blood collected upon enrolment. Disease incidence at the population level was estimated using a Bayesian mixture model.

FINDINGS

27 866 (33·8%) of 82 491 participants who met inclusion criteria were recruited. Blood cultures were performed for 27 544 (98·8%) of enrolled participants. Clinically significant organisms were detected in 2136 (7·7%) of these cultures, and 346 (16·2%) Salmonella enterica serovar Typhi were isolated. The overall adjusted incidence per 100 000 person-years of observation was highest in Kavuaya and Nkandu 1, Democratic Republic of the Congo (315, 95% credible interval 254-390). Overall, 46 (16·4%) of 280 tested isolates showed ciprofloxacin non-susceptibility.

INTERPRETATION

High disease incidence (ie, >100 per 100 000 person-years of observation) recorded in four countries, the prevalence of typhoid hospitalisations and complicated disease, and the threat of resistant typhoid strains strengthen the need for rapid dispatch and implementation of effective typhoid conjugate vaccines along with measures designed to improve clean water, sanitation, and hygiene practices.

FUNDING

The Bill & Melinda Gates Foundation.

Effect of single-dose, live, attenuated dengue vaccine in children with or without previous dengue on risk of subsequent, virologically confirmed dengue in Cebu, the Philippines: a longitudinal, prospective, population-based cohort study

BACKGROUND

A three-dose dengue vaccine (CYD-TDV) was licensed for use in children aged 9 years and older starting in 2015 in several dengue-endemic countries. In 2016, the Philippine Department of Health implemented a dengue vaccination programme, which was discontinued because of safety concerns. We assessed the relative risk of developing virologically confirmed dengue among children who did or did not receive a single dose of CYD-TDV by previous dengue virus (DENV) infections at baseline classified as none, one, and two or more infections.

METHODS

In this longitudinal, prospective, population-based cohort study, we enrolled healthy children (aged 9-14 years) residing in Bogo or Balamban, Cebu, Philippines, between May 2, and June 2, 2017, before a mass dengue vaccination campaign, via the Rural Health Unit in Bogo and three Rural Health Units in Balamban. We collected demographic information and sera for baseline DENV serostatus and conducted active surveillance for acute febrile illness. Children who developed acute febrile illness were identified, clinical data were collected, and blood was drawn for confirmation of dengue by RT-PCR. The primary outcome was the relative risk of developing virologically confirmed dengue among children who received or did not receive a single dose of CYD-TDV by DENV serostatus at baseline.

FINDINGS

A single dose of CYD-TDV did not confer protection against virologically confirmed dengue in children who had none or one previous DENV infection at baseline. One dose conferred significant protection against hospital admission for virologically confirmed dengue among participants who had two or more previous DENV infections at baseline during the first 3 years (70%, 95% CI 20-88; p=0·017) and the entire follow-up period (67%, 19-87; p=0·016).

INTERPRETATION

The risk of developing virologically confirmed dengue after a single dose of CYD-TDV varied by baseline DENV serostatus. Since the study assessed the effect of only a single dose, the findings cannot inform decisions on vaccination by public health officers. However, the findings have implications for children who receive an incomplete vaccination regimen and these results should prompt more detailed analyses in future trials on dengue vaccines.

FUNDING

The Philippine Department of Health, Hanako Foundation, WHO, Swedish International Development Cooperation Agency, International Vaccine Institute, University of North Carolina, and US National Institute of Allergy and Infectious Diseases.

Do Oral Cholera Vaccine and Water, Sanitation, and Hygiene Combine to Provide Greater Protection Against Cholera? Results From a Cluster-Randomized Trial of Oral Cholera Vaccine in Kolkata, India

Background

Oral cholera vaccine (OCV) and incremental improvements in household water, sanitation, and hygiene (WASH) within cholera-endemic areas can reduce cholera risk. However, we lack empiric evaluation of their combined impact.

Methods

We evaluated a cluster-randomized, placebo-controlled trial of OCV (Shanchol) in Kolkata, India. The study population included 108 777 individuals, and 106 879 nonpregnant individuals >1 year of age were eligible to receive 2 doses of OCV or placebo. We measured cholera risk in all household members assigned to OCV vs placebo and in all members of households with "Better" vs "Not Better" WASH, where WASH was classified according to validated criteria. Protection was measured by Cox proportional hazard models.

Results

Residence in an OCV household was associated with protective effectiveness (PE) of 54% (95% CI, 42%-64%; P < .001) and was similar regardless of Better (PE, 57%; 95% CI, 26%-75%; P = .002) or Not Better (PE, 53%; 95% CI, 40%-64%; P < .001) household WASH. Better WASH household residence was associated with PE of 30% (95% CI, 5%-48%; P = .023) and was similar in OCV (PE, 24%; 95% CI, -26% to 54%; P = .293) and placebo (PE, 29%; 95% CI, -3% to 51%; P = .069) households. When assessed conjointly, residence in OCV households with Better WASH was associated with the greatest PE against cholera at 69% (95% CI, 49%-81%; P < .001).

Conclusions

These findings suggest that the combination of a vaccine policy and improved WASH reduces cholera risk more than either would alone, although the magnitude of either intervention was not affected by the other. Future randomized trials investigating OCV and WASH interventions separately and together are recommended to further understand the interaction between OCV and WASH.

Association Among Household Water, Sanitation, and Hygiene (WASH) Status and Typhoid Risk in Urban Slums: Prospective Cohort Study in Bangladesh

BACKGROUND

Typhoid fever, or enteric fever, is a highly fatal infectious disease that affects over 9 million people worldwide each year, resulting in more than 110,000 deaths. Reduction in the burden of typhoid in low-income countries is crucial for public health and requires the implementation of feasible water, sanitation, and hygiene (WASH) interventions, especially in densely populated urban slums.

OBJECTIVE

In this study, conducted in Mirpur, Bangladesh, we aimed to assess the association between household WASH status and typhoid risk in a training subpopulation of a large prospective cohort (n=98,087), and to evaluate the performance of a machine learning algorithm in creating a composite WASH variable. Further, we investigated the protection associated with living in households with improved WASH facilities and in clusters with increasing prevalence of such facilities during a 2-year follow-up period.

METHODS

We used a machine learning algorithm to create a dichotomous composite variable ("Better" and "Not Better") based on 3 WASH variables: private toilet facility, safe drinking water source, and presence of water filter. The algorithm was trained using data from the training subpopulation and then validated in a distinct subpopulation (n=65,286) to assess its sensitivity and specificity. Cox regression models were used to evaluate the protective effect of living in "Better" WASH households and in clusters with increasing levels of "Better" WASH prevalence.

RESULTS

We found that residence in households with improved WASH facilities was associated with a 38% reduction in typhoid risk (adjusted hazard ratio=0.62, 95% CI 0.49-0.78; P<.001). This reduction was particularly pronounced in individuals younger than 10 years at the first census participation, with an adjusted hazard ratio of 0.49 (95% CI 0.36-0.66; P<.001). Furthermore, we observed an inverse relationship between the prevalence of "Better" WASH facilities in clusters and the incidence of typhoid, although this association was not statistically significant in the multivariable model. Specifically, the adjusted hazard of typhoid decreased by 0.996 (95% CI 0.986-1.006) for each percent increase in the prevalence of "Better" WASH in the cluster (P=.39).

CONCLUSIONS

Our findings demonstrate that existing variations in household WASH are associated with differences in the risk of typhoid in densely populated urban slums. This suggests that attainable improvements in WASH facilities can contribute to enhanced typhoid control, especially in settings where major infrastructural improvements are challenging. These findings underscore the importance of implementing and promoting comprehensive WASH interventions in low-income countries as a means to reduce the burden of typhoid and improve public health outcomes in vulnerable populations.

Better Existing Water, Sanitation, and Hygiene Can Reduce the Risk of Cholera in an Endemic Setting: Results From a Prospective Cohort Study From Kolkata, India

Background

Global cholera control efforts rely heavily on effective water, sanitation, and hygiene (WASH) interventions in cholera-endemic settings.

Methods

Using data from a large, randomized controlled trial of oral cholera vaccine conducted in Kolkata, India, we evaluated whether natural variations in WASH in an urban slum setting were predictive of cholera risk. From the control population (n = 55 086), baseline WASH data from a randomly selected "training subpopulation" (n = 27 634) were analyzed with recursive partitioning to develop a dichotomous ("better" vs "not better") composite household WASH variable from several WASH features collected at baseline, and this composite variable was then evaluated in a mutually exclusive "validation population" (n = 27 452). We then evaluated whether residents of better WASH households in the entire population (n = 55 086) experienced lower cholera risk using Cox regression models. Better WASH was defined by a combination of 4 dichotomized WASH characteristics including safe source of water for daily use, safe source of drinking water, private or shared flush toilet use, and always handwashing with soap after defecation.

Results

Residence in better WASH households was associated with a 30% reduction in risk of cholera over a 5-year period (adjusted hazard ratio, 0.70 [95% confidence interval, .49-.99]; P = .048). We also found that the impact of better WASH households on reducing cholera risk was greatest in young children (0-4 years) and this effect progressively declined with age.

Conclusions

The evidence suggests that modest improvements in WASH facilities and behaviors significantly modify cholera risk and may be an important component of cholera prevention and elimination strategies in endemic settings. Clinical Trials Registration. NCT00289224.

Statistical considerations on real time and extended controlled temperature conditions (ECTC) stability data analysis of vaccines

BACKGROUND

Although maintaining vaccines in a strict cold chain has cost and logistical implications in low- and middle-income countries, only a few vaccines have obtained approval for extended controlled temperature conditions (ECTC) application, which permits the administration of vaccines after storage outside of the cold chain for a defined period. We developed a methodology to evaluate stability data and calculate minimum release potency (MRP) in support of ECTC application.

METHODS

The methodology is focused on statistical considerations consisting of stability data collection, statistical analysis plan, statistical modelling, and statistical report. It uses mock stability data from a hypothetical product and may serve as a helpful guide for other products. The statistical data analysis is performed using the R program which is an open-source program and validated using the SAS software.

RESULTS

We developed a stability data testing scheme that included 24 lots with six-time points for up to 24 months under real-time and real condition (RT) in the cold chain samples stored at 2-8 °C and 12 lots with six timepoints for 14 days under ECTC samples stored at 40 °C. The log-transformed stability data met the linear regression assumptions and were poolable from representative lots with no significant lot variation. The linear regression analysis model with a common slope and intercept confirmed the stable antigen content over time under RT and ECTC by the mean regression line and 95% confidence interval. Based on the fitted models and the estimated coefficients, the antigen content value of 966 was derived as the MRP under RT for 24 months followed by 14 days under ECTC.

CONCLUSION

The presented framework of statistical considerations, with practical methods and R program codes to perform statistical analysis, may serve as a guide for developing the CTC data for a vaccine's stability evaluation prospectively.

Conducting a phase III clinical trial in children during the COVID- 19 pandemic: Experience and lessons learnt from a clinical research facility of Nepal

Clinical trials in humans are vital to test safety and efficacy of new interventions and are accompanied with the complexity of related regulatory guidelines, stringent time frame and financial burden particularly when participants are children. Conducting clinical trials in low and middle income countries, where 90% of global diseases occur, increases the complexity as resources, infrastructures, and experience related to clinical trials may be limited in some countries. During the COVID-19 pandemic, due to multiple infection control measures such as social distancing, lock-down of the societies, and increased work load of hospital workers, conducting clinical trials seemed very challenging. Related guidelines and recommendations on clinical trials required updates to adapt the situation for ongoing clinical trials to be continued and new clinical trials to be initiated. In this review report, we described the lessons learnt through our experiences, challenges we faced, and the mitigation measures implemented as a response while conducting a phase III clinical trial on a non-COVID-19 vaccine at a government children's hospital during the COVID-19 pandemic. We hope this report will contribute in lowering the obstacles to allow the successful completion of future studies, in countries where people live with the burden of vaccine-preventable diseases.

Assessment of vaccine herd protection in a cluster-randomised trial of Vi conjugate vaccine against typhoid fever: results of further analysis

Background

A cluster-randomised trial of Vi-tetanus toxoid (Vi-TT) conjugate vaccine conducted in urban Bangladeshi children found a high level of direct protection by Vi-TT but no significant vaccine herd protection. We reassessed the trial using a "fried egg" analysis to evaluate whether herd protection might have been obscured by transmission of typhoid into the clusters from the outside.

Methods

A participant- and observer-blind, cluster-randomised trial was conducted between February 14, 2018 and August 12, 2019 in three wards of Mirpur, a densely populated urban area of Dhaka, Bangladesh. Children 9 months to under 16 years of age in 150 geographic clusters, which had a total of 311,289 persons present at baseline or entering during follow-up, were randomised by cluster to a single-dose of Vi-TT or Japanese encephalitis (JE) vaccine. Vi-TT protection against typhoid fever, detected at 8 treatment centres serving the study population, was compared in the original clusters for the trial, and for progressively more central subclusters ("yolks" of the "fried egg") of the cluster residents. If transmission of typhoid into the clusters had diluted observed vaccine herd protection, we hypothesised that analysis of the innermost "yolks" would reveal vaccine herd protection that was not evident in analysis of the entire clusters. The trial is registered at www.isrctn.com as ISRCTN11643110.

Findings

At ≤18 months of follow-up, total vaccine effectiveness (protection of Vi-TT recipients relative to JE vaccine recipients) was 85% (95% CI: 76%, 90%); indirect effectiveness (protection of non-Vi-TT recipients in Vi-TT clusters relative to non-JE vaccine recipients in JE vaccine clusters) was 17% (95% CI: -13%, 40%); and overall effectiveness (protection of all residents in the Vi-TT clusters relative to all residents of the JE vaccine clusters) was 57% (95% CI: 44%, 66%). Analyses of subpopulations in inner 75%, 50% and 25% "yolks" of the clusters failed to reveal significant changes in any of these estimates.

Interpretation

Our analysis did not reveal Vi-TT herd protection in the trial. Consideration should be given to exploring whether targeting adults as well as children with Vi-TT yields appreciable levels of vaccine herd protection.

Funding

Bill & Melinda Gates Foundation (OPP1151153, INV-025388).

The interplay between WASH practices and vaccination with oral cholera vaccines in protecting against cholera in urban Bangladesh: Reanalysis of a cluster-randomized trial

The current global initiative to end Cholera by 2030 emphasizes the use of oral cholera vaccine (OCV) combined with feasible household Water-Sanitation-Hygiene (WASH) interventions. However, little is known about how improved WASH practices and behaviors and OCV interact to reduce the risk of cholera. We reanalyzed two arms of a cluster-randomized trial in urban Bangladesh, to evaluate the effectiveness of OCV given as a 2-dose regimen. One arm (30 clusters, n = 94,675) was randomized to vaccination of persons aged one year and older with OCV, and the other arm (30 clusters, n = 80,056) to no intervention. We evaluated the prevention of cholera by household WASH, classified at baseline using a previously validated rule, and OCV over 2 years of follow-up. When analyzed by assignment to OCV clusters rather than receipt of OCV, in comparison to persons living in "Not Better WASH" households in the control clusters, reduction of severe cholera (the primary outcome) was similar for persons in "Not Better WASH" households in vaccine clusters (46%, 95% CI:24,62), for persons in "Better WASH" households in the control clusters (48%, 95% CI:25,64), and for persons in "Better WASH" households in the vaccine clusters (48%, 95% CI:16,67). In contrast, when analyzed by actual receipt of a complete OCV regimen, , in comparison to persons in "Not Better WASH" households in the control clusters, protection against severe cholera increased steadily from 39% (95% CI:13,58) in residents of "Better WASH" households in the control clusters to 57% (95% CI:35,72) in vaccinated persons in "Not Better WASH" households to 63% (95% CI:21,83) in vaccinated persons in "Better WASH" households. This analysis suggests that improved household WASH and OCV received may interact to provide greater protection against cholera. However, the divergence between findings related to intent to vaccinate versus those pertaining to actual receipt of OCV underscores the need for further research on this topic.

Cost of oral cholera vaccine delivery in a mass immunization program for children in urban Bangladesh

Cholera poses a substantial health burden in the developing world due to both epidemic and endemic diseases. The World Health Organization recommends oral cholera vaccines for mass vaccination campaigns in addition to traditional prevention practices and treatments in resource-poor settings. In many developing countries like Bangladesh, the major challenge behind implementing mass vaccination campaigns concerns the affordability of the oral cholera vaccine (OCV). Vaccination of children with OCV is not only an impactful approach for controlling cholera at the population level and reducing childhood morbidity but is also considered more cost-effective than vaccinating all ages. The aim of the study was to estimate the cost of an OCV campaign for children from a societal perspective using empirical study. A total of 66,311 children aged 1 to 14 years old were fully vaccinated with two doses of the OCV Shanchol while 9,035 individuals received one dose of this vaccine. The estimated societal cost per individual for full vaccination was US$ 6.11, which includes the cost of vaccine delivery estimated at US$ 1.95. The cost per single dose was estimated at US$ 2.86. The total provider cost for full vaccination was estimated at US$ 6.01 and the recipient cost at US$ 0.10. Our estimation of OCV delivery costs for children was relatively higher than what was found in a similar mass OCV campaign for all age groups, indicating that there may be additional cost factors to consider in targeted vaccine campaigns. This analysis provides useful benchmarks for the possible costs related to delivery of OCV to children and future OCV cost-effectiveness models should factor in these possible cost disparities. Attempts to reduce the cost per dose are likely to have a greater impact on the cost of similar vaccination campaigns in many resource-poor settings.

Impact of vaccination with SCB-2019 COVID-19 vaccine on transmission of SARS-CoV-2 infection: a household contact study in the Philippines

Background

An exploratory household transmission study was nested in SPECTRA, the phase 2/3 efficacy study of the adjuvanted recombinant protein-based COVID-19 vaccine SCB-2019. We compared occurrence of confirmed COVID-19 infections between households and household contacts of infected SPECTRA placebo or SCB-2019 recipients.

Methods

SPECTRA participants at eight study sites in the Philippines who developed rRT-PCR-confirmed COVID-19 were contacted by a study team blinded to assignment of index cases to vaccine or placebo groups to enroll in this household transmission study. Enrolled households and household contacts were monitored for three weeks using rRT-PCR and anti-SARS-CoV-2 N-antigen IgG/IgM testing to detect new COVID-19 infections.

Results

154 eligible COVID-19 index cases (51 vaccinees, 103 placebo) were included. The secondary attack rate per household for symptomatic COVID-19 infection was 0.76% (90% CI: 0.15–3.90) if the index case was a SCB-2019 vaccinee compared with 5.88% (90% CI: 3.20–10.8) for placebo index cases, a relative risk reduction (RRR) of 79% (90% CI: -28–97). The RRR of symptomatic COVID-19 per household member was similar: 84% (90% CI: 28–97). Impact on attack rates in household members if index cases were symptomatic (n = 130; RRR = 80%; 90% CI: 7–96) or asymptomatic (n = 24; RRR = 100%; 90% CI: -76–100) was measurable but the low numbers undermine the clinical significance.

Conclusions

In this prospective household contact study vaccination with SCB-2019 reduced SARS-CoV-2 transmission compared with placebo in households and in household members independently of whether index cases were symptomatic or not.

Are better existing WASH practices in urban slums associated with a lower long-term risk of severe cholera? A prospective cohort study with 4 years of follow-up in Mirpur, Bangladesh

OBJECTIVE

To investigate the association between existing household water quality, sanitation and hygiene (WASH) practices and severe cholera risk in a dense urban slum where cholera is highly endemic.

DESIGN, SETTING AND PARTICIPANTS

We assembled a large prospective cohort within a cluster randomised trial evaluating the effectiveness of oral cholera vaccine. Our dynamic cohort population (n=193 576) comprised individuals living in the 'non-intervention' clusters of the trial, and were followed over 4 years. This study was conducted in a dense urban slum community of Dhaka, Bangladesh and cholera surveillance was undertaken in 12 hospitals serving the study area.

PRIMARY OUTCOME MEASURE

First severe cholera episode detected during follow-up period.

METHODS

We applied a machine learning algorithm on a training subpopulation (n=96 943) to develop a binary ('better', 'not better') composite WASH variable predictive of severe cholera. The WASH rule was evaluated for performance in a separate validation subpopulation (n=96 633). Afterwards, we used Cox regression models to evaluate the association between 'better' WASH households and severe cholera risk over 4 years in the entire study population.

RESULTS

The 'better' WASH rule found that water quality and access were the most significant factors associated with severe cholera risk. Members of 'better' WASH households, constituting one-third of the population, had a 47% reduced risk of severe cholera (95% CI: 29 to 69; p<0.001), after adjusting for covariates. The protective association between living in a 'better' WASH household and severe cholera persisted in all age groups.

CONCLUSIONS

Salutary existing household WASH practices were associated with a significantly reduced long-term risk of severe cholera in an urban slum of Dhaka. These findings suggest that WASH adaptations already practised in the community may be important for developing and implementing effective and sustainable cholera control programmes in similar settings.

TRIAL REGISTRATION NUMBER

This article is a re-analysis of data from a cluster randomized trial; can be found on ClinicalTrials.gov NCT01339845.

Immune non-interference and safety study of Vi-DT typhoid conjugate vaccine with a measles, mumps and rubella containing vaccine in 9-15 months old Nepalese infants

BACKGROUND

Typhoid fever is a common disease in developing countries especially in the Indian subcontinent and Africa. The available typhoid conjugate vaccines (TCV) have been found to be highly immunogenic in infants and children less than 2 years of age. Many countries are planning to adopt TCV in their routine EPI programs around 9 months of age when measles containing vaccines are given. Therefore, Vi-DT TCV was tested in 9-15 months aged healthy infants in Nepal to demonstrate non-interference with a measles containing vaccine.

METHODS

This was a randomized, open label, phase III study to assess the immune non-interference, safety, and reactogenicity of Vi-DT typhoid conjugate vaccine when given concomitantly with measles, mumps and rubella (MMR) vaccine. A total of 360 participants aged 9-15 months were enrolled and randomized equally into Vi-DT + MMR (180 participants) or MMR alone (180 participants) group and were evaluated for immunogenicity and safety 28 days post vaccination.

RESULTS

Using the immunogenicity set, difference between proportions (95% CI) of the Vi-DT + MMR group vs MMR alone group were -2.73% (-8.85, 3.38), -3.19% (-11.25, 4.88) and 2.91% (-3.36, 9.18) for sero-positivity rate of anti-measles, anti-mumps and anti- rubella, respectively. Only the lower bound of the range in difference of the proportions for sero-positivity rate of anti-mumps did not satisfy the non-inferiority criteria as it was above the -10% limit, which may not be of clinical significance. These results were confirmed in the per protocol set. There were no safety concerns reported from the study and both Vi-DT + MMR and MMR alone groups were comparable in terms of solicited and unsolicited adverse events .

CONCLUSIONS

Results indicated that there is non-interference of MMR vaccine with Vi-DT and Vi-DT conjugate vaccine could be considered as an addition to the EPI schedule among children at risk of contracting typhoid.

A Phase 3, Multicenter, Randomized, Controlled Trial to Evaluate Immune Equivalence and Safety of Multidose and Single-dose Formulations of Vi-DT Typhoid Conjugate Vaccine in Healthy Filipino Individuals 6 Months to 45 Years of Age

Trial Design

Phase 3, randomized, controlled, multicenter, equivalence trial.

Methods

Recruitment of participants occurred between 04Februray2020 and 15July2020 at four centers in the Philippines: University of the East - Ramon Magsaysay Memorial Medical Center Inc., Quezon City; University of Philippines Manila - National Institute of Health, Ermita Manila; Asian Hospital and Medical Center, Metro Manila, Philippines Study; and Medical Research Unit, Tropical Disease Foundation, Makati City, Metro Manila, Philippines.

Participants

1800 adults and children 6-months to 45-years of age.

Interventions

Participants received a single injection of multidose (MD) or single dose (SD) Vi-DT as test vaccines or meningococcal conjugate vaccine as a comparator.

Objective

To evaluate immune equivalence of SD and MD formulations of Vi-DT, and to assess the safety of both formulations compared with comparator vaccine.

Outcome Measurement

Blood draw for immunogenicity was performed at baseline prior to vaccine receipt and at four weeks after vaccination for a subset of participants to determine anti-Vi IgG geometric mean titers (GMT) and seroconversion rates. The primary outcome was comparison of anti Vi-IgG seroconversion and GMT between the two formulations of Vi-DT at 4 weeks following vaccine administration. Immune equivalence of MD and SD formulations was confirmed when the two-tailed 95% confidence interval (CI) of the GMT ratio is within [0.67, 1.5] at a two-sided significance level of 0.05. All participants were followed for safety events for six months after vaccine administration.

Randomization

Participants were randomized to receive SD Vi-DT, MD Vi-DT, or meningococcal conjugate vaccines in 2.5:2.5:1 allocation ratio.

Blinding

Study participants and observers were blinded to treatment assignment.

Findings

Immune equivalence of SD (n=252) and MD (n=247) formulations was confirmed by anti-Vi IgG GMT ratio of 1.14 (95%CI: 0.91, 1.43) with respective GMTs in the MD and SD groups of 640.62 IU/mL (95%CI: 546.39, 751.11) and 562.57 IU/mL (95%CI: 478.80, 661.00) (p=0.259). Similarly, anti-Vi IgG seroconversion rate difference between the two formulations of ‒0.43% (95%CI: -4.42, 3.56) confirmed immune equivalence with corresponding seroconversion rates of 98.38% (95%CI: 95.91, 99.37) and 98.81% (95%CI: 96.56, 99.59) in MD and SD Vi-DT formulations, respectively (p=0.722). Both formulations of Vi-DT had a satisfactory safety profile - all five serious adverse events reported during the study were unrelated to the investigational product.

Interpretation

The MD and SD formulations of Vi-DT elicited robust and equivalent immune responses following one dose vaccination, and both formulations demonstrated a favorable safety profile.

Trial Registration

ClinicalTrials.gov: NCT04204096.

Funding

This study was funded by the Bill & Melinda Gates Foundation (OPP 1115556).

Prevention of typhoid by Vi conjugate vaccine and achievable improvements in household WASH: Evidence from a cluster-randomized trial in Dhaka, Bangladesh

BACKGROUND

Typhoid fever contributes to approximately 135,000 deaths annually. Achievable improvements in household water-hygiene-sanitation (WASH) combined with vaccination using typhoid conjugate vaccines (TCVs) may be an effective preventive strategy. However, little is known about how improved WASH and vaccination interact to lower the risk of typhoid.

METHODS

61,654 urban Bangladeshi children aged 9 months to <16 years, residing in 150 clusters with a baseline population of 205,760 residents, were randomized 1: 1 by cluster to Vi-tetanus toxoid TCV or Japanese Encephalitis (JE) vaccine. Surveillance for blood culture-confirmed typhoid fever was conducted over two years. Existing household WASH status was assessed at baseline as Better or Not Better using previously validated criteria. The reduction in typhoid risk among all residents associated with living in TCV clusters, Better WASH households, or both was evaluated using mixed-effects Poisson regression models.

RESULTS

The adjusted reduced risk of typhoid among all residents living in the clusters assigned to TCV was 55% (95% confidence interval (CI): 43%,65%; p < 0.001), and that of living in Better WASH households, regardless of cluster, was 37% (95%CI: 24%,48%; p < 0.001). The highest risk of typhoid was observed in persons living in households with Not Better WASH in the JE clusters. In comparison with these persons, those living in households with Better WASH in the TCV clusters had an adjusted reduced risk of 71% (95%CI: 59%, 80%; p < 0.001).

CONCLUSION

Implementation of TCV programs combined with achievable and culturally acceptable household WASH practices were independently associated with a significant reduction in typhoid risk.

Safety and immunogenicity of the Vi-DT typhoid conjugate vaccine in healthy volunteers in Nepal: an observer-blind, active-controlled, randomised, non-inferiority, phase 3 trial

Background

Methods

Findings

Interpretation

Funding

Translation

Prevention of Typhoid Fever by Existing Improvements in Household Water, Sanitation, and Hygiene, and the Use of the Vi Polysaccharide Typhoid Vaccine in Poor Urban Slums: Results from a Cluster-Randomized Trial

Modest improvements in household water, sanitation, and hygiene (WASH) and typhoid vaccination can reduce typhoid risk in endemic settings. However, empiric evaluation of their combined impact is lacking. A total of 62,756 persons residing in 80 clusters in a Kolkata slum were allocated randomly 1:1 to either the typhoid Vi polysaccharide (ViPS) vaccine or hepatitis A (Hep A) vaccine. Surveillance was conducted for 2 years before and 2 years after vaccination. We classified households as having "better" or "not better" WASH, and calculated the prevalence of better WASH households in clusters using previously validated criteria. We evaluated the protection by better household WASH, better household WASH prevalence, and ViPS vaccination against typhoid in all cluster members present at baseline using Cox proportional hazard models. Overall, ViPS vaccination was associated with a 55% (P < 0.001; 95% CI, 35-69) reduction of typhoid risk and was similar regardless of better WASH in the residence. Living in a better WASH household was associated with a typhoid risk reduction of 31% (P = 0.16; 95% CI, -16 to 59) overall. The reduction was 48% (P = 0.05; 95% CI, -1 to 73) in Hep A clusters, 6% (P = 0.85; 95% CI, -82 to 51) in ViPS clusters, and 57% (P < 0.05; 95% CI, 15-78) in the population during the 2 years preceding the trial. These findings demonstrate a preventive association of better household WASH in the non-ViPS population, but, unexpectedly, an absence of additional protection from ViPS by better WASH in the ViPS population. This analysis highlights the importance of assessing the combination of WASH in conjunction with typhoid vaccines, and has implications for the evaluation of new-generation typhoid conjugate vaccines.

A non-inferiority trial comparing two killed, whole cell, oral cholera vaccines (Cholvax vs. Shanchol) in Dhaka, Bangladesh

Bangladesh remains cholera endemic with biannual seasonal peaks causing epidemics. At least 300,000 severe cases and over 4,500 deaths occur each year. The available oral cholera vaccineshave not yet been adopted for cholera control in Bangladesh due to insufficient number of doses available for endemic control. With a public private partnership, icddr,b initiated a collaboration between vaccine manufacturers in Bangladesh and abroad. A locally manufactured Oral Cholera Vaccine (OCV) named Cholvax became available for testing in Bangladesh. We evaluated the safety and immunogenicity of this locally produced Cholvax (Incepta Vaccine Ltd) inexpensive OCV comparatively to Shanchol (Shantha Biotechnics-Sanofi Pasteur) which is licensed in several countries. We conducted a randomized non-inferiority clinical trial of bivalent, killed oral whole-cell cholera vaccine Cholvax vs. Shanchol in the cholera-endemic area of Mirpur, Dhaka, among three different age cohorts (1-5, 6-17 and 18-45 years) between April 2016 and April 2017. Two vaccine doses were given at 14 days apart to 2,052 healthy participants. No vaccine-related serious adverse events were reported. There were no significant differences in the frequency of solicited (7.31% vs. 6.73%) and unsolicited (1.46% vs. 1.07%) adverse events reported between the Cholvax and Shanchol groups. Vibriocidal antibody responses among the overall population for O1 Ogawa (81% vs. 77%) and O1 Inaba (83% vs. 84%) serotypes showed that Cholvax was non-inferior to Shanchol, with the non-inferiority margin of -10%. For O1 Inaba, GMT was 462.60 (Test group), 450.84 (Comparator group) with GMR 1.02(95% CI: 0.92, 1.13). For O1 Ogawa, GMT was 419.64 (Test group), 387.22 (Comparator group) with GMR 1.12 (95% CI: 1.02, 1.23). Cholvax was safe and non-inferior to Shanchol in terms of immunogenicity in the different age groups. These results support public use of Cholvax to contribute for reduction of the cholera burden in Bangladesh. ClinicalTrials.gov number: NCT027425581.

Differential characteristics associated with progression of mitral and aortic regurgitation in patients undergoing kidney transplantation

Background

Heart valve regurgitation is common in patients with end-stage renal disease (ESRD). However, there are no data on the fate of mitral regurgitation (MR) and aortic regurgitation (AR) after kidney transplantation (KT). In this study, we sought to investigate regression or progression rates of MR and AR after KT in patients with ESRD. Moreover, we aimed to explore clinical and echocardiographic factors associated with the progression of MR and AR in patients undergoing KT.

Methods

Among 1,734 patients who underwent KT from 2005 to 2018 at a single tertiary hospital, 674 patients (407 men; mean 48±12 years) who underwent both pre- and post-KT echocardiography were analyzed comprehensively. Pre-KT echocardiography was performed within three months of KT, and post-KT echocardiography was done between 6 months and 24 months after KT. Severities of MR and AR were graded as no/trivial, mild, moderate, and severe according to the current guidelines. Regression was defined if the severity decreased by one or more grades, while progression was defined if the severity increased by one or more grades.

Results

Figure 1 shows the regression or progression of MR and AR after KT. 78 (11%) patients showed MR regression, but 41 (6%) experienced MR progression. 13 (2%) revealed AR regression, while 23 (4%) presented AR progression. In patients with MR progression, there were more cases of receiving a second KT, having mitral annular calcification, and showing lesser reduction of left atrial volume after KT. Patients with AR progression showed a longer hemodialysis duration, persistent hypertension after KT, and aortic root dilatation. Factors related to the progression of MR and AR showed statistically meaningful predictive values in a stepwise manner (Figure 2)

Conclusions

In patients undergoing KT, MR and AR may progress in patients with certain distinct characteristics. Different clinical and echocardiographic characteristics before KT, and reduction of hemodynamic loads after KT determine the progression of MR and AR. Further echocardiographic surveillances after KT are needed in patients with clinical and echocardiographic factors for progression of valve regurgitation.

Funding Acknowledgement

Type of funding sources: None.

Can Existing Improvements of Water, Sanitation, and Hygiene (WASH) in Urban Slums Reduce the Burden of Typhoid Fever in These Settings?

BACKGROUND

Sustained investments in water, sanitation, and hygiene (WASH) have lagged in resource-poor settings; incremental WASH improvements may, nonetheless, prevent diseases such as typhoid in disease-endemic populations.

METHODS

Using prospective data from a large cohort in urban Kolkata, India, we evaluated whether baseline WASH variables predicted typhoid risk in a training subpopulation (n = 28 470). We applied a machine learning algorithm to the training subset to create a composite, dichotomous (good, not good) WASH variable based on 4 variables, and evaluated sensitivity and specificity of this variable in a validation subset (n = 28 470). We evaluated in Cox regression models whether residents of "good" WASH households experienced a lower typhoid risk after controlling for potential confounders. We constructed virtual clusters (radius 50 m) surrounding each household to evaluate whether a prevalence of good WASH practices modified the typhoid risk in central household members.

RESULTS

Good WASH practices were associated with protection in analyses of all households (hazard ratio [HR] = 0.57; 95% confidence interval [CI], .37-.90; P = .015). This protection was evident in persons ≥5 years old at baseline (HR = 0.47; 95% CI, .34-.93; P = .005) and was suggestive, though not statistically significant, in younger age groups (HR = 0.61; 95% CI, .27-1.38; P = .235). The level of surrounding household good WASH coverage was also associated with protection (HR = 0.988; 95% CI, .979-.996; P = .004, for each percent coverage increase). However, collinearity between household WASH and WASH coverage prevented an assessment of their independent predictive contributions.

CONCLUSIONS

In this typhoid-endemic setting, natural variation in household WASH was associated with typhoid risk. If replicated elsewhere, these findings suggest that WASH improvements may enhance typhoid control, short of major infrastructural investments.

Effectiveness of a killed whole-cell oral cholera vaccine in Bangladesh: further follow-up of a cluster-randomised trial

BACKGROUND

Killed whole-cell oral cholera vaccines (OCVs) are widely used for prevention of cholera in developing countries. However, few studies have evaluated the protection conferred by internationally recommended OCVs for durations beyond 2 years of follow-up.

METHODS

In this study, we followed up the participants of a cluster-randomised controlled trial for 2 years after the end of the original trial. Originally, we had randomised 90 geographical clusters in Dhaka slums in Bangladesh in equal numbers (1:1:1) to a two-dose regimen of OCV alone (targeted to people aged 1 year or older), a two-dose regimen of OCV plus a water-sanitation-hygiene (WASH) intervention, or no intervention. There was no masking of group assignment. The WASH intervention conferred little additional protection to OCV and was discontinued at 2 years of follow-up. Surveillance for severe cholera was continued for 4 years. Because of the short duration and effect of the WASH intervention, we combined the two OCV intervention groups. The primary outcomes were OCV overall protection (protection of all members of the intervention clusters) and total protection (protection of individuals who got vaccinated in the intervention clusters) against severe cholera, which we assessed by multivariable survival models appropriate for cluster-randomised trials. This trial is registered on ClinicalTrials.gov, NCT01339845.

FINDINGS

The study was done between April 17, 2011, and Nov 1, 2015. 268 896 participants were present at the time of the first dose, with 188 206 in the intervention group and 80 690 in the control group. OCV coverage of the two groups receiving OCV was 66% (123 659 of 187 214 participants). During 4 years of follow-up, 441 first episodes of severe cholera were detected (243 episodes in the vaccinated groups and as 198 episodes in the unvaccinated group). Overall OCV protection was 36% (95% CI 19 to 49%) and total OCV protection was 46% (95% CI 32 to 58). Cumulative total vaccine protection was notably lower for people vaccinated before the age of 5 years (24%; -30 to 56) than for people vaccinated at age 5 years or older (49%; 35 to 60), although the differences in protection for the two age groups were not significant (p=0·3308). Total vaccine protection dropped notably (p=0·0115) after 3 years in children vaccinated at 1-4 years of age.

INTERPRETATION

These findings provide further evidence of long-term effectiveness of killed whole-cell OCV, and therefore further support for the use of killed whole-cell OCVs to control endemic cholera, but indicate that protection is shorter-lived in children vaccinated before the age of 5 years than in people vaccinated at the age of 5 years or older.

FUNDING

Bill & Melinda Gates Foundation.

TRANSLATION

For the Bengali translation of the abstract see Supplementary Materials section.

Safety and immunogenicity of Vi-DT conjugate vaccine among 6-23-month-old children: Phase II, randomized, dose-scheduling, observer-blind Study

BACKGROUND

Typhoid causes significant mortality among young children in resource-limited settings. Conjugate typhoid vaccines could significantly reduce typhoid-related child deaths, but only one WHO-prequalified typhoid conjugate vaccine exists for young children. To address this gap, we investigated the safety, immunogenicity and dose-scheduling of Vi-DT typhoid conjugate vaccine among children aged 6-23 months.

METHODS

In this single center, observer blind, phase II trial, participants were randomly assigned (2:2:1) to receive one or two doses of Vi-DT or comparator vaccine. Anti-Vi IgG titer and geometric mean titers (GMT) were determined at 0, 4, 24 and 28 weeks. Data were analyzed using per-protocol and immunogenicity (a subset of intention-to-treat analysis) sets. The trial is registered with ClinicalTrials.gov (NCT03527355).

FINDINGS

Between April and July 2018, 285 children were randomized; 114 received one or two doses of Vi-DT while 57 received comparator. 277 completed the study follow-up per protocol; 112 and 110 from single- and two-dose Vi-DT schedules, respectively and 55 from the placebo group were included in the per protocol analysis. Safety profile is satisfactory. Thirteen serious adverse events were reported during the 28-week follow-up, none of which were related to Vi-DT. The seroconversion rate four weeks after the first dose was 100% (95% CI 98·3-100) in Vi-DT recipients and 7·0% (95% CI 2·8-16·7) in comparator recipients (p<0·0001). Similarly, the seroconversion rate 4 weeks after the second dose was 98·2% (95% CI 93· 6-99·5) and 21·8% (95% CI 13·0-34·4) among Vi-DT and comparator groups, respectively (p<0·0001). Anti-Vi IgG GMT was significantly higher in Vi-DT than in control group at all post-vaccination visits (p<0·0001).

INTERPRETATION

Both single and two doses of Vi-DT vaccine are safe, well tolerated, and immunogenic for infants and toddlers in a moderately endemic setting.

Use of Typhoid Vi-Polysaccharide Vaccine as a Vaccine Probe to Delineate Clinical Criteria for Typhoid Fever

Blood cultures (BCs) detect an estimated 50% of typhoid fever cases. There is need for validated clinical criteria to define cases that are BC negative, both to help direct empiric antibiotic treatment and to better evaluate the magnitude of protection conferred by typhoid vaccines. To derive and validate a clinical rule for defining BC-negative typhoid fever, we assessed, in a cluster-randomized effectiveness trial of Vi-polysaccharide (ViPS) typhoid vaccine in Kolkata, India, 14,797 episodes of fever lasting at least 3 days during 4 years of comprehensive, BC-based surveillance of 70,865 persons. A recursive partitioning algorithm was used to develop a decision rule to predict BC-proven typhoid cases with a diagnostic specificity of 97–98%. To validate this rule as a definition for BC-negative typhoid fever, we assessed whether the rule defined culture-negative syndromes prevented by ViPS vaccine. In a training subset of individuals, we identified the following two rules: rule 1: patients aged < 15 years with prolonged fever accompanied by a measured body temperature ≥ 100°F, headache, and nausea; rule 2: patients aged ≥ 15 years with prolonged fever accompanied by nausea and palpable liver but without constipation. The adjusted protective efficacy of ViPS against clinical typhoid defined by these rules in persons aged ≥ 2 years in a separate validation subset was 33% (95% CI: 4–53%). We have defined and validated a clinical rule for predicting BC-negative typhoid fever using a novel vaccine probe approach. If validated in other settings, this rule may be useful to guide clinical care and to enhance typhoid vaccine evaluations.

Unmasking herd protection by an oral cholera vaccine in a cluster-randomized trial

Background

Several studies have shown that inactivated, whole-cell oral cholera vaccines (OCVs) confer both direct protection on vaccinees and herd protection on populations. Because our earlier cluster-randomized effectiveness trial (CRT) in urban Bangladesh failed to detect OCV herd protection, we reanalysed the trial to assess whether herd effects were masked in our original analysis.

Methods

A total of 267 270 persons were randomized to 90 approximately equal-sized clusters. In 60 clusters persons aged 1 year and older were eligible to receive OCV and in 30 clusters persons received no intervention and served as controls. We analysed OCV protection against severely dehydrating cholera for the entire clusters, as in our original analysis, and for subclusters consisting of residents of innermost households. We hypothesized that if OCV herd protection was attenuated by cholera transmission into the clusters from the outside in this densely populated setting, herd protection would be most evident in the innermost households.

Results

During 2 years of follow-up of all residents of the clusters, total protection (protection of OCV recipients relative to control residents) was 58% [95% confidence interval (CI): 43%, 70%; P<0.0001], indirect protection (protection of non-OCV recipients in OCV clusters relative to control participants) was 16% (95% CI: –20%, 41%; P=0.35) and overall OCV protection (protection of all residents in the OCV clusters relative to control residents) was 46% (95% CI: 30%, 59%; P<0.0001). Analyses of the inner 75% and 50% households of the clusters showed similar findings. However, total protection was 75% (95% CI: 50%, 87%, P<0.0001), indirect protection 52% (95% CI: –9%, 79%; P=0.08) and overall protection 72% (95% CI: 49%, 84%; P<0.0001) for the innermost 25% households.

Conclusion

Consistent with past studies, substantial OCV herd protective effects were identified, but were unmasked only by analysing innermost households of the clusters. Caution is needed in defining clusters for analysis of vaccine herd effects in CRTs of vaccines.

Re-evaluating herd protection by Vi typhoid vaccine in a cluster randomized trial

Background

In a cluster randomized trial (CRT) of a Vi polysaccharide vaccine against typhoid in the slums of Kolkata we found evidence of vaccine herd protection. However, transmission of typhoid into clusters from the outside likely occurred in this densely populated setting, which could have diminished our estimates of vaccine herd protection.

Methods

Eighty clusters (40 in each arm) were randomised to receive a single dose of either Vi or inactivated hepatitis A vaccine. We analysed protection for the entire cluster and for subclusters consisting of residents of the innermost households.

Results

During 2 y of follow-up, total protection was 61% (95% CI 41 to 75), overall protection was 57% (95% CI 37 to 71) and indirect protection was 44% (95% CI 2 to 69). Analyses of the innermost 75% and 50% of households of the clusters showed similar findings. However, in the innermost 25% of households of the clusters, total protection was 82% (95% CI 48 to 94) and overall protection was 66% (95% CI 27 to 84). There was not a sufficient sample size to demonstrate such a trend for indirect protection in these innermost households.

Conclusions

The findings suggest that analyses of the entire cluster may have led to underestimation of herd protection against typhoid by Vi vaccine and that restriction of the analyses to the inner subclusters may have led to a more accurate estimation of vaccine herd effects.

Comparison of anti-Vi IgG responses between two clinical studies of typhoid Vi conjugate vaccines (Vi-DT vs Vi-TT)

Salmonella enterica serovar Typhi (S. Typhi) is a causative agent for typhoid fever and especially critical in developing countries. Although clinical studies for various typhoid conjugate vaccines (TCVs) have been performed, there are no comparative data on the immune responses of vaccines due to lack of harmonization of the serological assay. Recently, Typbar-TCV (Vi-TT) was prequalified by WHO and recommended for vaccination in endemic areas. Forty-eight serum samples were selected from a recent Vi-DT phase 1 study based on age cohort and anti-Vi IgG levels using an in-house ELISA. Anti-Vi IgG titers of 48 sera were also determined by Vacczyme ELISA, used in a Vi-TT phase 3 trial. A good correlation between the two assays was observed when the anti-Vi IgG titer was determined using Vacczyme ELISA based on the Vi-IgG_R1,2011, U.S. reference reagent (Pearson correlation coefficient (r) = 0.991, P < 0.001) or Vacczyme ELISA calibrator (r = 0.991, P < 0.001). Based on the correlation, multiple linear regression model was developed to convert data of 281 sera (prior to vaccination and 28 days post first-dose) in the Vi-DT phase 1 study from in-house ELISA titers to Vacczyme ELISA values and then, compared with the Vi-TT results. Similar estimates of anti-Vi IgG GMT were observed after vaccination with the Vi-DT and Vi-TT vaccines [1626 EU/ml (95% CI: 1292–2047) vs 1293 EU/ml (95% CI: 1153–1449), respectively]. The method used here can be implemented to estimate and compare anti-Vi IgG levels between different clinical studies of TCVs. This approach enables comparison of the antibody responses among TCVs under development and may help facilitate licensing of new TCVs.

Typhoid fever is an infectious and life-threatening disease in developing countries. Before 2017, Ty21a and Vi polysaccharide vaccines were licensed but these are not recommended in young children under 2-year-old. Vaccine manufacturers are developing typhoid Vi conjugate vaccines (TCVs) to improve immunogenicity. Typbar-TCV (Vi-TT) demonstrated its safety and immunogenicity in infants and recently, prequalified by WHO. Serum Vi-specific IgG antibody has been used to measure the immunogenicity of TCV in many clinical trials. However, due to lack of harmonized assay, comparison of the immunogenicity among various TCVs is not possible in the absence of head-to-head clinical trials. Recently, we evaluated immunogenicity of Vi-DT using an in-house ELISA in the clinical study. In this study, 48 sera were selected from Vi-DT phase 1 study and measured anti-Vi IgG using commercial Vacczyme ELISA kit, used in the phase 3 study of Vi-TT, to compare the immunogenicity between two vaccines. Based on the correlation between two assays, anti-Vi IgG of all participants in the Vi-DT study was converted to Vacczyme antibody value using statistical model and compared with results of Vi-TT phase 3 study. The antibody levels induced by two studies were similar in pre- and post-vaccinated sera. This approach enables to compare the antibody responses among TCVs under development and would facilitate licensing of new TCVs.

Augmented immune responses to a booster dose of oral cholera vaccine in Bangladeshi children less than 5 years of age: Revaccination after an interval of over three years of primary vaccination with a single dose of vaccine

We have earlier reported that a single dose of oral cholera vaccine (OCV) is protective in adults and children ≥5 years of age and sustained for 2 years. We enrolled participants (n = 240) from this study, between March-September 2017, over 3 years after receiving a primary single dose. Immune responses were measured in placebo group (Primary Immunization group: PI) and compared with those who received a single dose (Booster Immunization group: BI). The children were 4 to <5 years, 5 to <18 years and adults >18 years. Blood was collected at day 0 (before vaccination) and after receiving 1st and 2nd doses of OCV. Overall, the BI and PI groups showed vibriocidal antibody response after 1st and 2nd dose of vaccination in all age groups to V. cholerae O1 and O139. Young children in the BI group showed significantly higher vibriocidal antibody response two weeks after receiving the first dose as compared to PI group to LPS. Elevated plasma IgA responses to LPS after the first dose were observed among the BI group compared to the PI group among the young children. Mucosal antibody responses measured in fecal extracts showed similar increases as that of vibriocidal and LPS responses in the BI group. These results suggest a single boosting dose of OCV generated immune response in primed population >5 years of age who had earlier received OCV. However, young children who had received OCV earlier, boosting after a single dose, resulted in increased immune responses compared to the PI group. Further studies are needed to assess protection obtained from different strategies, especially for young children and to determine the numbers of primary and booster doses needed. In addition, more information is needed regarding the optimum interval between primary and booster doses to plan future interventions for cholera control. ClinicalTrials.gov Identifier: NCT02027207.

Immunogenicity, safety and reactogenicity of a Phase II trial of Vi-DT typhoid conjugate vaccine in healthy Filipino infants and toddlers: A preliminary report

BACKGROUND

Typhoid fever remains an important public health problem in developing countries and is endemic in many parts of Asia and Africa where the incidence of disease typically peaks in school-aged children. Age restrictions and other limitations of existing oral live-attenuated typhoid and parenteral Vi polysaccharide vaccines have triggered the development of Vi conjugate vaccines with improved immunological properties, use in younger age range, and longer durability of protection. We present the safety, reactogenicity, and immunogenicity data from a Phase II study after a single dose of Vi polysaccharide conjugated to diphtheria toxoid (Vi-DT) conducted in 6-23-month old Filipino children.

METHODS

This is a randomized, observer-blinded Phase II study to assess the immunogenicity, safety and reactogenicity of Vi-DT compared to placebo, conducted in Muntinlupa City, The Philippines. Participants aged 6-23 months were enrolled and randomized to Vi-DT (25 µg) or placebo (0.9% sodium chloride) and evaluated for immunogenicity and overall safety 28 days post vaccination.

RESULTS

A total of 285 participants were enrolled and age-stratified: 6 to < 9 months, 9-12 months, and 13-23 months. Seventy-six (76) participants received Vi-DT and 19 received placebo per each strata. All participants seroconverted after a single dose of Vi-DT versus 7% of placebo recipients. Anti-Vi IgG GMT was 444.38 [95% CI (400.28; 493.34)] after a single dose of Vi-DT; there was no change in GMT after placebo administration, 0.41 [95% CI (0.33; 0.51), p < 0.0001]. A similar pattern of immunogenicity was reported across all age strata. The vaccine reported to be safe and well tolerated.

CONCLUSIONS

Vi-DT vaccine was immunogenic, safe, and well tolerated in children aged 6-23 months. ClinicalTrials.gov registration number: NCT03527355.

Safety and immunogenicity of a killed bivalent (O1 and O139) whole-cell oral cholera vaccine in adults and children in Vellore, South India

This open-label study assessed the safety and immunogenicity of two doses (14 days apart) of an indigenously manufactured, killed, bivalent (Vibrio cholerae O1 and O139), whole-cell oral cholera vaccine (SHANCHOL; Shantha Biotechnics) in healthy adults (n = 100) and children (n = 100) in a cholera endemic area (Vellore, South India) to fulfill post-licensure regulatory requirements and post-World Health Organization (WHO) prequalification commitments. Safety and reactogenicity were assessed, and seroconversion rates (i.e. proportion of participants with a ≥ 4-fold rise from baseline in serum vibriocidal antibody titers against V. cholerae O1 Inaba, O1 Ogawa and O139, respectively) were determined 14 days after each vaccine dose. No serious adverse events were reported during the study. Commonly reported solicited adverse events were headache and general ill feeling. Seroconversion rates after the first and second dose in adults were 67.7% and 55.2%, respectively, against O1 Inaba; 47.9% and 45.8% against O1 Ogawa; and 19.8% and 20.8% against O139. In children, seroconversion rates after the first and second dose were 80.2% and 68.8%, respectively, against O1 Inaba; 72.9% and 67.7% against O1 Ogawa; and 26.0% and 18.8% against O139. The geometric mean titers against O1 Inaba, O1 Ogawa, and O139 in both adults and children were significantly higher after each vaccine dose compared to baseline titers (P < 0.001; for both age groups after each dose versus baseline). The seroconversion rates for O1 Inaba, O1 Ogawa, and O139 in both age groups were similar to those in previous studies with the vaccine. In conclusion, the killed, bivalent, whole-cell oral cholera vaccine has a good safety and reactogenicity profile, and is immunogenic in healthy adults and children. Trial Registration: ClinicalTrials.gov NCT00760825; CTRI/2012/01/002354.

Safety of a bivalent, killed, whole-cell oral cholera vaccine in pregnant women in Bangladesh: evidence from a randomized placebo-controlled trial

BACKGROUND

Cholera increases the risk of harmful effects on foetuses. We prospectively followed pregnant women unaware of their pregnancy status who received a study agent in a clinical trial evaluating the association between exposure to an oral cholera vaccine (OCV) and foetal survival.

METHODS

Study participants were selected from a randomized placebo-controlled trial conducted in Dhaka, Bangladesh. The vaccination campaign was conducted between January 10 and February 4, 2014. We enrolled women who were exposed to an OCV or placebo during pregnancy (Cohort 1) and women who were pregnant after the vaccination was completed (Cohort 2). Our primary endpoint was pregnancy loss (spontaneous miscarriage or stillbirth), and the secondary endpoints were preterm delivery and low birth weight. We employed a log-binomial regression to calculate the relative risk of having adverse outcomes among OCV recipients compared to that among placebo recipients.

RESULT

There were 231 OCV and 234 placebo recipients in Cohort 1 and 277 OCV and 299 placebo recipients in Cohort 2. In Cohort 1, the incidence of pregnancy loss was 113/1000 and 115/1000 among OCV and placebo recipients, respectively. The adjusted relative risk for pregnancy loss was 0.97 (95% CI: 0.58-1.61; p = 0.91) in Cohort 1. We did not observe any variation in the risk of pregnancy loss between the two cohorts. The risks for preterm delivery and low birth weight were not significantly different between the groups in both cohorts.

CONCLUSIONS

Our study provides additional evidence that exposure to an OCV during pregnancy does not increase the risk of pregnancy loss, preterm delivery, or low birth weight, suggesting that pregnant women in cholera-affected regions should not be excluded in a mass vaccination campaign.

TRIAL REGISTRATION

The study is registered at ( http://clinicaltrials.gov ). Identifier: NCT02027207 .

In vitro Mycobacterial Growth Inhibition in South Korean Adults With Latent TB Infection

Background: It is important to understand the ability to inhibit mycobacterial growth in healthy adults who would have been Bacillus Calmette-Guérin (BCG) vaccinated in childhood as this group will be the potential target population for novel booster TB vaccine trials. In this study we investigated not only the long-term immunity induced by childhood BCG vaccination but also protective immunity in terms of the ability to inhibit mycobacterial growth in those who were BCG vaccinated in childhood, with evidence of recent or remote TB infection. Methods: We measured the baseline immune response using a functional mycobacterial growth inhibition assay (MGIA) as a novel approach and an intracellular cytokine staining (ICS) assay as a reference approach in healthy adults, with different status of Mycobacterium tuberculosis (Mtb) infection. Results: Based on MGIA responses in historically BCG-vaccinated healthy adults, demographical characteristics including age, and gender did not affect mycobacterial growth inhibition in PBMC. However, the uninfected healthy control (HC) group showed a greater ability to inhibit mycobacterial growth compared with the latent TB infection (LTBI) group (P = 0.0005). In terms of the M. tuberculosis antigen-specific T-cell immune response in diluted whole blood quantitated using an ICS assay, the LTBI group had a higher frequency of polyfunctional CD 4+ T cells compared with the HC group (P = 0.0002), although there was no correlation between ICS and the MGIA assay. Conclusion: The Mtb infection status had a significant impact on mycobacterial growth inhibition in PBMC from healthy adults in South Korea, a country with an intermediate burden of tuberculosis, with healthy controls showing the greatest mycobacterial growth inhibition.

Use of oral cholera vaccine as a vaccine probe to determine the burden of culture-negative cholera

Analyses of stool from patients with acute watery diarrhea (AWD) using sensitive molecular diagnostics have challenged whether fecal microbiological cultures have acceptably high sensitivity for cholera diagnosis. If true, these findings imply that current estimates of the global burden of cholera, which rely largely on culture-confirmation, may be underestimates. We conducted a vaccine probe study to evaluate this possibility, assessing whether an effective killed oral cholera vaccine (OCV) tested in a field trial in a cholera-endemic population conferred protection against cholera culture-negative AWD, with the assumption that if cultures are indeed insensitive, OCV protection in such cases should be detectable. We re-analysed the data of a Phase III individually-randomized placebo-controlled efficacy trial of killed OCVs conducted in Matlab, Bangladesh in 1985. We calculated the protective efficacy (PE) of a killed whole cell-only (WC-only) OCV against first-episodes of cholera culture-negative AWD during two years of post-dosing follow-up. In secondary analyses, we evaluated PE against cholera culture-negative AWD by age at vaccination, season of onset, and disease severity. In this trial 50,770 people received at least 2 complete doses of either WC-only OCV or placebo, and 791 first episodes of AWD were reported during the follow-up period, of which 365 were culture-positive for Vibrio cholerae O1. Of the 426 culture-negative AWD episodes, 215 occurred in the WC group and 211 occurred in the placebo group (adjusted PE = -1.7%; 95%CI -23.0 to 13.9%, p = 0.859). No measurable PE of OCV was observed against all or severe cholera culture-negative AWD when measured overall or by age and season subgroups. In this OCV probe study we detected no vaccine protection against AWD episodes for which fecal cultures were negative for Vibrio cholera O1. Results from this setting suggest that fecal cultures from patients with AWD were highly sensitive for cholera episodes that were etiologically attributable to this pathogen. Similar analyses of other OCV randomized controlled trials are recommended to corroborate these findings.

Conventional microbiological culture has remained a relatively uncontested ‘gold standard’ for the diagnosis of cholera; however, emerging methods, including sensitive molecular tests, challenge the current paradigm. One pivotal article demonstrated that culture failed to detect cholera in one-third of the cholera-positive stool specimens confirmed by other methods. This finding underscored the absence of a reliable reference test, further complicated by newer tests outperforming the gold standard, leaving no suitable comparator. In this study, we used oral cholera vaccine as a probe to investigate the reliability of conventional culture as a diagnostic for cholera by measuring the effectiveness of the vaccine against cholera culture-negative acute watery diarrhea. We did not find any evidence of protection, implying that the culture diagnostics used were reliable. The dynamics of cholera transmission require a rapid response, and ascertaining the best rapid diagnostic test for early detection of outbreaks will maximize the effectiveness of chronically limited resources in high risk regions. As techniques advance, well-designed studies should be implemented to systematically evaluate their merit against established methods, and improved diagnostics, including rapid diagnostics and microbiological culture, should be implemented into cholera control programs to reduce cholera transmission by creating a better trigger for outbreak response.

Safety and immunogenicity of a Vi-DT typhoid conjugate vaccine: Phase I trial in Healthy Filipino adults and children

BACKGROUND

Typhoid fever remains a major public health problem in low- and middle-income countries where children aged 2-14 years bear the greatest burden. Vi polysaccharide is poorly immunogenic in children <2 years of age, and protection in adults is modest. The limitations of Vi polysaccharide vaccines can be overcome by conjugation of the Vi to a carrier protein. A typhoid conjugate vaccine composed of Vi polysaccharide conjugated to diphtheria toxoid (Vi-DT) has been developed. The Phase I study results are presented here.

METHODS

This was a randomized, observer-blinded Phase I study to assess the safety and immunogenicity of Vi-DT compared to Vi polysaccharide vaccine, conducted in Manila, Philippines. Participants enrolled in an age de-escalation manner (18-45, 6-17 and 2-5 years) were randomized between Test (Vi-DT, 25 µg) administered at 0 and 4 weeks and Comparator (Vi polysaccharide, Typhim Vi® and Vaxigrip®, Sanofi Pasteur) vaccines.

RESULTS

A total of 144 participants were enrolled (48 by age strata, 24 in Test and Comparator groups each). No serious adverse event was reported in either group. Solicited and unsolicited adverse events were mild or moderate in both groups with the exception of a 4-year old girl in Test group with grade 3 fever which resolved without sequelae. All participants in Test group seroconverted after first and second doses of Vi-DT while the proportions in the Comparator group were 97.1% and 97.2%, after first dose of Typhim Vi® and second dose of Vaxigrip®, respectively. Vi-DT showed 4-fold higher Geometric Mean Titers (GMT) compared to Typhim Vi® (adjusted for age strata, p < 0.001). No further increase of GMT was detected after the second dose of Vi-DT. Anti-DT IgG seroresponse rates were 81.2% and 84.5% post first and second Vi-DT doses, respectively.

CONCLUSIONS

Vi-DT vaccine was safe, well-tolerated and immunogenic in participants aged 2-45 years. ClinicalTrials.gov registration number: NCT02645032.

A randomized, observer-blinded, equivalence trial comparing two variations of Euvichol®, a bivalent killed whole-cell oral cholera vaccine, in healthy adults and children in the Philippines

•

Bridging study demonstrating the equivalence of two variations of Euvichol®.

•

The 600L thimerosal-free Euvichol® is safe and immunogenic in adults and children.

•

The scale-up of Euvichol® allows expanding global access to oral cholera vaccine.

Background

To contribute to the global demand for oral cholera vaccine (OCV), the production of Euvichol® was scaled up with elimination of thimerosal. To demonstrate the equivalence of the variations, a study was carried out in the Philippines.

Methods

Healthy male and female adults and children in Manila were randomized to receive two doses of Euvichol® two weeks apart from either the 100L (Comparator) or the 600L (Test) variation. Primary and secondary immunogenicity endpoints were respectively geometric mean titer (GMT) of vibriocidal antibodies (two weeks post second dose) and seroconversion rate (two weeks after each dose) against O1 Inaba, Ogawa, and O139 serogroups. The GMT of vibriocidal antibodies against O1 Inaba, Ogawa, and O139 two weeks post first dose was also measured. To show the equivalence of two variations of Euvichol®, the ratio of GMT and the difference of seroconversion rate between Test and Comparator vaccines were tested with equivalence margin of [0.5, 2.0] for GMT ratio and of 15% for seroconversion rate, respectively. Safety assessment included solicited reactogenicity within 6 days after each dose and unsolicited and serious adverse events.

Results

A total of 442 participants were enrolled. For the overall population, equivalence between Test and Comparator was demonstrated for vibriocidal antibody response against O1 Inaba and Ogawa serotypes and O139 serogroup in both modified intention-to-treat (mITT) and per protocol analysis, since the 95% confidence intervals (CI) of GMT to any serotypes were within the lower and upper boundary [0.5, 2.0]. Seroconversion rates after two doses also showed equivalence for O1 Inaba, Ogawa, and O139. The vaccine was safe and well tolerated, similarly between the two groups.

Conclusion

The study results support the equivalence of the 600L Euvichol® to the 100L formulation in healthy children and adults. The 600L Euvichol® is safe and immunogenic in adults and children.

ClinicalTrials.gov registration number: NCT02502331.

Validation and comparison of ELISA kits to measure interferon gamma responses in QuantiFERON cultural supernatants for diagnosis of tuberculosis

Much effort has been made to reduce the cost of LTBI diagnosis with equivalent efficacy and efficiency of interferon-γ release assay (IGRA). This study showed that repeatability, intermediate precision, and accuracy of the Bionote-ELISA were comparable to QFT-ELISA. The Bionote-ELISA could provide the alternative method.

Efficacy of a single-dose regimen of inactivated whole-cell oral cholera vaccine: results from 2 years of follow-up of a randomised trial

BACKGROUND

A single-dose regimen of inactivated whole-cell oral cholera vaccine (OCV) is attractive because it reduces logistical challenges for vaccination and could enable more people to be vaccinated. Previously, we reported the efficacy of a single dose of an OCV vaccine during the 6 months following dosing. Herein, we report the results of 2 years of follow-up.

METHODS

In this placebo-controlled, double-blind trial done in Dhaka, Bangladesh, individuals aged 1 year or older with no history of receipt of OCV were randomly assigned to receive a single dose of inactivated OCV or oral placebo. The primary endpoint was a confirmed episode of non-bloody diarrhoea for which the onset was at least 7 days after dosing and a faecal culture was positive for Vibrio cholerae O1 or O139. Passive surveillance for diarrhoea was done in 13 hospitals or major clinics located in or near the study area for 2 years after the last administered dose. We assessed the protective efficacy of the OCV against culture-confirmed cholera occurring 7-730 days after dosing with both crude and multivariable per-protocol analyses. This trial is registered at ClinicalTrials.gov, number NCT02027207.

FINDINGS

Between Jan 10, 2014, and Feb 4, 2014, 205 513 people were randomly assigned to receive either vaccine or placebo, of whom 204 700 (102 552 vaccine recipients and 102 148 placebo recipients) were included in the per-protocol analysis. 287 first episodes of cholera (109 among vaccine recipients and 178 among placebo recipients) were detected during the 2-year follow-up; 138 of these episodes (46 in vaccine recipients and 92 in placebo recipients) were associated with severe dehydration. The overall incidence rates of initial cholera episodes were 0·22 (95% CI 0·18 to 0·27) per 100 000 person-days in vaccine recipients versus 0·36 (0·31 to 0·42) per 100 000 person-days in placebo recipients (adjusted protective efficacy 39%, 95% CI 23 to 52). The overall incidence of severe cholera was 0·09 (0·07 to 0·12) per 100 000 person-days versus 0·19 (0·15 to 0·23; adjusted protective efficacy 50%, 29 to 65). Vaccine protective efficacy was 52% (8 to 75) against all cholera episodes and 71% (27 to 88) against severe cholera episodes in participants aged 5 years to younger than 15 years. For participants aged 15 years or older, vaccine protective efficacy was 59% (42 to 71) against all cholera episodes and 59% (35 to 74) against severe cholera. The protection in the older age groups was sustained throughout the 2-year follow-up. In participants younger than 5 years, the vaccine did not show protection against either all cholera episodes (protective efficacy -13%, -68 to 25) or severe cholera episodes (-44%, -220 to 35).

INTERPRETATION

A single dose of the inactivated whole-cell OCV offered protection to older children and adults that was sustained for at least 2 years. The absence of protection of young children might reflect a lesser degree of pre-existing natural immunity in this age group.

FUNDING

Bill & Melinda Gates Foundation to the International Vaccine Institute.

Antibody secreting B cells and plasma antibody response to rotavirus vaccination in infants from Kolkata India

Background

Assessing immune response after rotavirus vaccination consists in measuring serum or plasma IgA and IgG antibodies, but these assays provide very little information about the mucosal immune response. Thus the development of assays for detection of mucosal immune response following rotavirus vaccination is essential. We evaluate to assess circulating antibody-secreting cells (ASCs) as a potential means to evaluate mucosal immune responses to rotavirus vaccine.

Methods

372 subjects, aged 6 weeks, were enrolled in the study. All the subjects were assigned to receive two doses of Rotarix^® vaccine. Using a micro-modified whole blood-based ELISPOT assay, circulating rotavirus type-specific IgA- and IgG-ASCs, including gut homing β7+ ASCs, were enumerated on week 6 before the first dose of Rotarix vaccination at 7 weeks of age and week 18 after the second vaccination at 17 weeks of age. Plasma samples collected before vaccination, and after two doses of Rotarix^® vaccination were tested for plasma rotavirus IgA titers.

Results

Two doses of Rotarix^® provided to induce sero-protective titer of ≥ 20 Units in 35% of subjects. Total blood IgA- ASC responses were detected in 26.4% of subjects who were non-responder before vaccination. Among responders, 47% of the subjects also have sero-protective plasma IgA titers.

Discussion

Our results suggest that virus-specific blood gut homing ASCs were detected and provide insight into mucosal immune response after rotavirus vaccination. Further studies are needed to evaluate the duration of such immune responses and to assess the programmatic utility of this whole blood-based mucosal ASC testing for the rotavirus immunization program.

Use of oral cholera vaccine as a vaccine probe to define the geographical dimensions of person-to-person transmission of cholera

Background

Cholera is known to be transmitted from person to person, and inactivated oral cholera vaccines (OCVs) have been shown to confer herd protection via interruption of this transmission. However, the geographic dimensions of chains of person-to-person transmission of cholera are uncertain. The ability of OCVs to confer herd protection was used to define these dimensions in two cholera-endemic settings, one in rural Bangladesh and the other in urban India.

Methods

Two large randomized, placebo-controlled trials of inactivated OCVs, one in rural Matlab, Bangladesh and the other in urban Kolkata, India, were reanalyzed. Vaccine herd protection was evaluated by relating the risk of cholera in placebo recipients to vaccine coverage of surrounding residents residing within concentric rings. In Matlab, concentric rings in 100-m increments up to 700 m were evaluated; in Kolkata, 50-m increments up to 350m were evaluated.

Results

One hundred and eight cholera cases among 24 667 placebo recipients were detected during 1 year of post-vaccination follow-up at Matlab; 128 cholera cases among 34 968 placebo recipients were detected during 3 years of follow-up in Kolkata. Consistent inverse relationships were observed between vaccine coverage of the ring and the risk of cholera in the central placebo recipient for rings with radii up to 500 m in Matlab and up to 150 m in Kolkata.

Conclusions

These results suggest that the dimensions of chains of person-to-person transmission in endemic settings can be quite large and may differ substantially from setting to setting. Using OCVs as 'probes' to define these dimensions can inform geographical targeting strategies for the deployment of these vaccines in endemic settings.

Influence of maternal and socioeconomic factors on breast milk fatty acid composition in urban, low-income families

The lipid composition of breast milk may have a significant impact on early infant growth and cognitive development. Comprehensive breast milk data is lacking from low‐income populations in the Indian subcontinent impeding assessment of deficiencies and limiting development of maternal nutritional interventions. A single breast milk specimen was collected within 6 weeks postpartum from two low‐income maternal cohorts of exclusively breastfed infants, from Dhaka, Bangladesh (n = 683) and Kolkata, India (n = 372) and assayed for percentage composition of 26 fatty acids. Mature milk (>15 days) in Dhaka (n = 99) compared to Kolkata (n = 372) was higher in total saturated fatty acid (SFA; mean 48% vs. 44%) and disproportionately lower in ω3‐polyunsaturated fatty acid (PUFA), hence the ω6‐ and ω3‐PUFA ratio in Dhaka were almost double the value in Kolkata. In both sites, after adjusting for days of lactation, increased maternal education was associated with decreased SFA and PUFA, and increasing birth order or total pregnancies was associated with decreasing ω6‐PUFA or ω3‐PUFA by a factor of 0.95 for each birth and pregnancy. In Dhaka, household prosperity was associated with decreased SFA and PUFA and increased ω6‐ and ω3‐PUFA. Maternal height was associated with increased SFA and PUFA in Kolkata (1% increase per 1 cm), but body mass index showed no independent association with either ratio in either cohort. In summary, the socioeconomic factors of maternal education and household prosperity were associated with breast milk composition, although prosperity may only be important in higher cost of living communities. Associated maternal biological factors were height and infant birth order, but not adiposity. Further study is needed to elucidate the underlying mechanisms of these effects.

Comparison of IPV to tOPV week 39 boost of primary OPV vaccination in Indian infants: an open labelled randomized controlled trial

Background

The final endgame strategy of global polio eradication initiative includes switching from trivalent oral poliovirus vaccines (tOPV) to bivalent oral polio vaccine (bOPV), and introduction of inactivated poliovirus vaccine (IPV). This study compares IPV with tOPV week 39 boost in Indian infants.

Methods

Starting 28 March 2012, we enrolled 372 Indian infant-mother pairs from Kolkata, India in an open-label, block-randomized, controlled trial comparing a 39 week tOPV to an IPV boost among infants immunized with three doses of tOPV. The primary outcome was mucosal immunity to poliovirus as measured by fecal polio virus shedding after OPV challenge. The secondary outcome was humoral response as defined by >1:8 titers for neutralizing antibodies at week 40. Seroconversion was measured by change in level of antibody titers from week 18 to week 40. The analyses were performed by both intention-to-treat (ITT) and per-protocol (PP) comparing the occurrences of outcomes between the arms of the study.

Findings

Both the study arms provided equivalent mucosal immunity at 52 weeks with a total shedding prevalence of 28%. Vaccination with IPV resulted in significantly higher seroconversion rates for Polio type 2 (p = 0.03) and Polio type 3 (p < 0.01).

Conclusions

This study indicates that an IPV boost at week 39 is equivalent to tOPV in intestinal immunity, and provides higher seroconversion compared to tOPV. The major limitation of the study was the additional OPV doses receive by infants during pulse polio immunization resulted in additional mucosal boosting, diminishing the impact of IPV or tOPV boost at week 39. However, IPV for OPV boost should prove to be a step forward in the global polio eradication initiative to reduce the problem of circulating vaccine-derived poliovirus (cVDPV).

Potential for Controlling Cholera Using a Ring Vaccination Strategy: Re-analysis of Data from a Cluster-Randomized Clinical Trial

INTRODUCTION

Vaccinating a buffer of individuals around a case (ring vaccination) has the potential to target those who are at highest risk of infection, reducing the number of doses needed to control a disease. We explored the potential vaccine effectiveness (VE) of oral cholera vaccines (OCVs) for such a strategy.

METHODS AND FINDINGS

This analysis uses existing data from a cluster-randomized clinical trial in which OCV or placebo was given to 71,900 participants in Kolkata, India, from 27 July to 10 September 2006. Cholera surveillance was then conducted on 144,106 individuals living in the study area, including trial participants, for 5 y following vaccination. First, we explored the risk of cholera among contacts of cholera patients, and, second, we measured VE among individuals living within 25 m of cholera cases between 8 and 28 d after onset of the index case. For the first analysis, individuals living around each index case identified during the 5-y period were assembled using a ring to define cohorts of individuals exposed to cholera index cases. An index control without cholera was randomly selected for each index case from the same population, matched by age group, and individuals living around each index control were assembled using a ring to define cohorts not exposed to cholera cases. Cholera attack rates among the exposed and non-exposed cohorts were compared using different distances from the index case/control to define the rings and different time frames to define the period at risk. For the VE analysis, the exposed cohorts were further stratified according to the level of vaccine coverage into high and low coverage strata. Overall VE was assessed by comparing the attack rates between high and low vaccine coverage strata irrespective of individuals' vaccination status, and indirect VE was assessed by comparing the attack rates among unvaccinated members between high and low vaccine coverage strata. Cholera risk among the cohort exposed to cholera cases was 5-11 times higher than that among the cohort not exposed to cholera cases. The risk gradually diminished with an increase in distance and time. The overall and indirect VE measured between 8 and 28 d after exposure to a cholera index case during the first 2 y was 91% (95% CI 62%-98%) and 93% (95% CI 44%-99%), respectively. VE persisted for 5 y after vaccination and was similar whether the index case was a young child (<5 y) or was older. Of note, this study was a reanalysis of a cholera vaccine trial that used two doses; thus, a limitation of the study relates to the assumption that a single dose, if administered quickly, will induce a similar level of total and indirect protection over the short term as did two doses.

CONCLUSIONS

These findings suggest that high-level protection can be achieved if individuals living close to cholera cases are living in a high coverage ring. Since this was an observational study including participants who had received two doses of vaccine (or placebo) in the clinical trial, further studies are needed to determine whether a ring vaccination strategy, in which vaccine is given quickly to those living close to a case, is feasible and effective.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00289224.

Use of the data system for field management of a clinical study conducted in Kolkata, India

Background

Designing an appropriate data system is important to the success of a clinical study. However, little information is available on this topic. We share our experiences on designing, developing, and implementation of a data system for management of data and field activities of a complex clinical study.

Methods

The data system was implemented aiming at determining the biological basis for the underperformance of oral vaccines, such as polio and rotavirus vaccines in children at a site in Kolkata, India. The system included several functionalities to control data and field activities. It was restricted to authorized users based on their access privileges. A relational database platform was chosen, and Microsoft Visual FoxPro 7.0 (Microsoft Corporation, Seattle, WA, USA) was used to develop the system. The system was installed at the clinic and data office to facilitate both the field and data management activities.

Results

Data were doubly entered by two different data operators to identify keypunching errors in the data. Outliers, duplication, inconsistencies, missing entries, and linkage were also checked. Every modification and users log-in/log-out information was auto-recorded in an audit trail. The system offered tools for preparation of visit schedule of the participants. A visit considered as protocol deviation was documented by the system. The system alerted field staff to every upcoming visit date to organize the field activities and to inform participants which day to come. The system also produced a growth chart for evaluating nutritional status and referring the child to a specialized clinic if found to be severely malnourished.

Conclusion

The data system offered unique features for controlling for both data and field activities, which led to minimize drop-out rates as well as protocol deviations. Such system is warranted for a successful clinical study.

Comparison of immune responses to a killed bivalent whole cell oral cholera vaccine between endemic and less endemic settings

Studies on safety, immunogenicity and efficacy of the killed, bivalent whole cell oral cholera vaccine (Shanchol) have been conducted in historically endemic settings of Asia. Recent cholera vaccination campaigns in Haiti and Guinea have also demonstrated favourable immunogenicity and effectiveness in nonendemic outbreak settings. We performed a secondary analysis, comparing immune responses of Shanchol from two randomised controlled trials performed in an endemic and a less endemic area (Addis Ababa) during a nonoutbreak setting. While Shanchol may offer some degree of immediate protection in primed populations living in cholera endemic areas, as well as being highly immunogenic in less endemic settings, understanding the characteristics of immune responses in each of these areas is vital in determining ideal dosing strategies that offer the greatest public health impact to populations from areas with varying degrees of cholera endemicity.

Validity of the estimates of oral cholera vaccine effectiveness derived from the test-negative design

BACKGROUND

The test-negative design (TND) has emerged as a simple method for evaluating vaccine effectiveness (VE). Its utility for evaluating oral cholera vaccine (OCV) effectiveness is unknown. We examined this method's validity in assessing OCV effectiveness by comparing the results of TND analyses with those of conventional cohort analyses.

METHODS

Randomized controlled trials of OCV were conducted in Matlab (Bangladesh) and Kolkata (India), and an observational cohort design was used in Zanzibar (Tanzania). For all three studies, VE using the TND was estimated from the odds ratio (OR) relating vaccination status to fecal test status (Vibrio cholerae O1 positive or negative) among diarrheal patients enrolled during surveillance (VE= (1-OR)×100%). In cohort analyses of these studies, we employed the Cox proportional hazard model for estimating VE (=1-hazard ratio)×100%).

RESULTS

OCV effectiveness estimates obtained using the TND (Matlab: 51%, 95% CI:37-62%; Kolkata: 67%, 95% CI:57-75%) were similar to the cohort analyses of these RCTs (Matlab: 52%, 95% CI:43-60% and Kolkata: 66%, 95% CI:55-74%). The TND VE estimate for the Zanzibar data was 94% (95% CI:84-98%) compared with 82% (95% CI:58-93%) in the cohort analysis. After adjusting for residual confounding in the cohort analysis of the Zanzibar study, using a bias indicator condition, we observed almost no difference in the two estimates.

CONCLUSION

Our findings suggest that the TND is a valid approach for evaluating OCV effectiveness in routine vaccination programs.

A randomized, non-inferiority trial comparing two bivalent killed, whole cell, oral cholera vaccines (Euvichol vs Shanchol) in the Philippines

BACKGROUND

Currently, there are two oral cholera vaccines (OCV) that are prequalified by the World Health Organization. Both (Dukoral and Shanchol) have been proven to be safe, immunogenic, and effective. As the global supply of OCV remains limited, we assessed the safety and immunogenicity of a new low cost, killed, bivalent OCV (Euvichol) in the Philippines.

METHODS

The randomized controlled trial was carried out in healthy Filipino adults and children. Two doses of either the current WHO prequalified OCV (Shanchol) or the same composition OCV being considered for WHO prequalification (Euvichol) were administered to participants.

RESULTS

The pivotal study was conducted in total of 1263 healthy participants (777 adults and 486 children). No serious adverse reactions were elicited in either vaccine groups. Vibriocidal antibody responses to V. cholerae O1 Inaba following administration of two doses of Euvichol were non-inferior to those of Shanchol in adults (82% vs 76%) and children (87% vs 89%). Similar findings were observed for O1 Ogawa in adults (80% vs 74%) and children (91% vs 88%).

CONCLUSION

A two dose schedule with Euvichol induces a strong vibriocidal response comparable to those elicited by the currently WHO prequalified OCV, Shanchol. Euvichol will be an oral cholera vaccine suitable for use in lower income countries, where cholera still has a significant economic and public health impact.

Peru-15 (Choleragarde(®)), a live attenuated oral cholera vaccine, is safe and immunogenic in human immunodeficiency virus (HIV)-seropositive adults in Thailand

BACKGROUND

Many areas with endemic and epidemic cholera report significant levels of HIV transmission. According to the World Health Organization (WHO), over 95% of reported cholera cases occur in Africa, which also accounts for nearly 70% of people living with HIV/AIDS globally. Peru-15, a promising single dose live attenuated oral cholera vaccine (LA-OCV), was previously found to be safe and immunogenic in cholera endemic areas. However, no data on the vaccine's safety among HIV-seropositive adults had been collected.

METHODS

This study was a double-blinded, individually randomized, placebo-controlled trial enrolling HIV-seropositive adults, 18-45 years of age, conducted in Bangkok, Thailand, to assess the safety of Peru-15 in a HIV-seropositive cohort.

RESULTS

32 HIV infected subjects were randomized to receive either a single oral dose of the Peru-15 vaccine with a buffer or a placebo (buffer only). No serious adverse events were reported during the follow-up period in either group. The geometric mean fold (GMF) rise in V. cholerae O1 El Tor specific antibody titers between baseline and 7 days after dosing was 32.0 (p<0.001) in the vaccine group compared to 1.6 (p<0.14) in the placebo group. Among the 16 vaccinees,14 vaccinees (87.5%) had seroconversion compared to 1 of 16 placebo recipients (6.3%). V. cholerae was isolated from the stool of one vaccinee, and found to be genetically identical to the Peru-15 vaccine strain. There were no significant changes in HIV viral load or CD4 T-cell counts between vaccine and placebo groups.

CONCLUSION

Peru-15 was shown to be safe and immunogenic in HIV-seropositive Thai adults.

A Randomized, Placebo-Controlled Trial Evaluating Safety and Immunogenicity of the Killed, Bivalent, Whole-Cell Oral Cholera Vaccine in Ethiopia

Killed whole-cell oral cholera vaccine (OCV) has been a key component of a comprehensive package including water and sanitation measures for recent cholera epidemics. The vaccine, given in a two-dose regimen, has been evaluated in a large number of human volunteers in India, Vietnam, and Bangladesh, where it has demonstrated safety, immunogenicity, and clinical efficacy. We conducted a double-blind randomized placebo-controlled trial in Ethiopia, where we evaluated the safety and immunogenicity of the vaccine in 216 healthy adults and children. OCV was found to be safe and elicited a robust immunological response against Vibrio cholerae O1, with 81% adults and 77% children demonstrating seroconversion 14 days after the second dose of vaccine. This is the first study to evaluate safety and immunogenicity of the vaccine in a population outside Asia using a placebo-controlled, double-blind, randomized study design.

An Open Label Non-inferiority Trial Assessing Vibriocidal Response of a Killed Bivalent Oral Cholera Vaccine Regimen following a Five Year Interval in Kolkata, India

BACKGROUND

The bivalent killed oral cholera vaccine (OCV) provides 65% cumulative protection over five years. It remains unknown whether a boosting regimen can maintain protection in previously immunized populations. This study examines the immunogenicity and safety of an OCV regimen given five years following initial dosing.

METHODOLOGY/PRINCIPAL FINDINGS

An open label controlled trial was conducted in 426 healthy Indian participants previously enrolled in a large efficacy trial. To assess whether an OCV regimen given after five years can elicit an antibody response equal to that of a primary series, we compared vibriocidal antibody titers in previously immunized participants receiving a two dose booster regimen to participants receiving a primary two dose immunization series. Among participants receiving a two dose primary series of OCV (n = 186), 69% (95% CI 62%-76%) seroconverted. In the intervention arm (n = 184), 66% (95% CI 59%-73%) seroconverted following a two dose boosting schedule given five years following the initial series. Following a single boosting dose, 71% (95% CI 64%-77%) seroconverted. Children demonstrated 79% (95% CI 69%-86%) and 82% (95% CI 73%-88%) seroconversion after primary and boosting regimens, respectively.

CONCLUSIONS/SIGNIFICANCE

Administration of an OCV boosting regimen elicits an immune response similar to those receiving a primary series in endemic areas. Though a single boosting dose induces a strong immune response, further investigations are needed to measure if these findings translate to clinical protection.

Flexibility of oral cholera vaccine dosing-a randomized controlled trial measuring immune responses following alternative vaccination schedules in a cholera hyper-endemic zone

BACKGROUND

A bivalent killed whole cell oral cholera vaccine has been found to be safe and efficacious for five years in the cholera endemic setting of Kolkata, India, when given in a two dose schedule, two weeks apart. A randomized controlled trial revealed that the immune response was not significantly increased following the second dose compared to that after the first dose. We aimed to evaluate the impact of an extended four week dosing schedule on vibriocidal response.

METHODOLOGY/PRINCIPAL FINDINGS

In this double blind randomized controlled non-inferiority trial, 356 Indian, non-pregnant residents aged 1 year or older were randomized to receive two doses of oral cholera vaccine at 14 and 28 day intervals. We compared vibriocidal immune responses between these schedules. Among adults, no significant differences were noted when comparing the rates of seroconversion for V. cholerae O1 Inaba following two dose regimens administered at a 14 day interval (55%) vs the 28 day interval (58%). Similarly, no differences in seroconversion were demonstrated in children comparing the 14 (80%) and 28 day intervals (77%). Following 14 and 28 day dosing intervals, vibriocidal response rates against V. cholerae O1 Ogawa were 45% and 49% in adults and 73% and 72% in children respectively. Responses were lower for V. cholerae O139, but similar between dosing schedules for adults (20%, 20%) and children (28%, 20%).

CONCLUSIONS/SIGNIFICANCE

Comparable immune responses and safety profiles between the two dosing schedules support the option for increased flexibility of current OCV dosing. Further operational research using a longer dosing regimen will provide answers to improve implementation and delivery of cholera vaccination in endemic and epidemic outbreak scenarios.