Effectiveness of pentavalent rotavirus vaccine in a large urban population in the United States

Effectiveness of Lanzhou Lamb Rotavirus Vaccine and RotaTeq Against Hospitalized Rotavirus Infections Among Children During 2020-2023 in Guangdong Province, China: A Test-Negative Case-Control Study

INTRODUCTION

The evidence regarding the effectiveness of Lanzhou Lamb Rotavirus Vaccine (LLR) and RotaTeq (RV5) against gastroenteritis (RVGE) caused by emerging genotypes in Chinese children remains limited.

METHODS

We conducted a test-negative case-control study using gastroenteritis surveillance data from four cities (2020-2023) in Guangdong Province, China. Children aged 2 months to 5 years hospitalized with acute gastroenteritis were enrolled. Cases were rotavirus-positive; controls were rotavirus-negative. Vaccine effectiveness (VE) was estimated using multivariable logistic regressions.

RESULTS

Among 2650 children, 218 (8.2%) were rotavirus-positive, predominantly G8P[8]. Also, 1543 (58.23%) children were unvaccinated, while 632 (23.85%) and 475 (17.92%) received at least one dose of RV5 and LLR, respectively. Adjusted RV5 VE against any RVGE severity was 51.7% [95% confidence interval (CI) - 58.1-85.3%]) for one dose, 37.6% (95% CI - 58.5-75.4%) for two doses, and 64.1% (95% CI 38.0-79.2%) for three doses. For LLR, VE against any RVGE severity was 38.7% (95% CI 5.7-60.2%) for one dose, 74.6% (95% CI 35.3-90.0%) for two doses, and 58.8% (95% CI - 217.6-94.6%) for three doses. Against severe RVGE, RV5 VE was 67.2% (95% CI - 144.7-95.6%) for one dose, 74.0% (95% CI - 92.1-96.5%) for two doses, and 86.6% (95% CI 56.8-95.9%) for three doses. For LLR, VE against severe RVGE was 57.7% (95% CI 20.3-77.6%) for one dose, 73.4% (95% CI 11.9-92.0%) for two doses, and - 27.8% (95% CI - 949.7-84.4%) for three doses.

CONCLUSIONS

Both RV5 and LLR provided protection against RVGE, including the emerging G8P[8] genotype. Three doses of RV5 offered strong protection, while two doses of LLR also appeared to be an effective strategy against rotavirus infection.

Assessment of the Impact of the Rotavirus Vaccine Against Severe Rotaviral Diarrhea in Uzbekistan

BACKGROUND

This article presents the results of a long-term study of the impact of rotavirus vaccination in Uzbekistan. Uzbekistan is the first country in the Central Asian region to introduce rotavirus vaccination into the national compulsory vaccination calendar. The study aimed to evaluate the impact of rotavirus vaccination on hospitalizations due to all-cause AGE and RVGE in children < 5 years of age in Uzbekistan.

METHODS

Detection of rotavirus antigen was performed using Rotavirus-Antigen-IFA-BEST "Vector Best" kit (Novosibirsk, Russia).

RESULTS

The total of 20,128 children under 5 years of age were hospitalized in sentinel hospitals with a diagnosis of acute gastroenteritis during the study period (2019-2020). Of this number of children, 4481 children (22.2%) were included in the study. Of 4481 children, 367 (8.2%) children tested positive for rotavirus. In our study, decrease in the rotavirus rate was noted in all age groups. The peak of rotavirus positivity occurred in the months of January and February.

CONCLUSION

The average rotavirus-positive rate in the period (2019-2020) was 8.2% and the absolute percentage decrease was 18.1% compared to the pre-vaccination period (2005-2009) where the rotavirus-positive rate was 26.3%. The percentage of prevented cases averaged 68.8%.

Impact after the Change from Voluntary to Universal Oral Rotavirus Vaccination on Consecutive Emergency Department Visits for Acute Gastroenteritis among Children in Kobe City, Japan (2016-2022)

Rotavirus (RV) is the leading cause of acute gastroenteritis (AGE), particularly in infants. In 2006, the high efficacy of oral RV vaccines (RVVs, RotarixTM and RotaTeqTM) was demonstrated. Voluntary RVV started in Japan in 2011, and in October 2020 were launched as universal oral RVVs in Japan. However, the impact of changes from voluntary to universal RVVs has not been studied in a primary emergency medical center in Japan. We investigated changes in the number of pediatric patients with AGE after introducing universal RVVs in our center. A clinical database of consecutive patients aged <16 who presented to Kobe Children’s Primary Emergency Medical Center between 1 April 2016 and 30 June 2022 was reviewed. After implementing universal RVVs, fewer children presented with RV-associated AGE (the reduction of proportion of the patients in 2022 was −61.7% (all ages), −57.9% (<1 years), −67.8% (1−<3 years), and −61.4% (3−<5 years) compared to 2019). A similar decrease in those of age who were not covered by the universal RVV was observed. There was a significant decline in the number of patients with AGE during the RV season who presented to the emergency department after implementing universal RVVs.

Do Rotavirus Strains Affect Vaccine Effectiveness? A Systematic Review and Meta-analysis

BACKGROUND

Rotavirus causes 215,000 deaths from severe childhood diarrhea annually. Concerns exist that a monovalent vaccine (RV1) and a pentavalent vaccine (RV5) may be less effective against rotavirus strains not contained in the vaccines. We estimated the vaccine effectiveness (VE) of RV1 and RV5 against severe rotavirus gastroenteritis caused by vaccine (homotypic) and nonvaccine (partially and fully heterotypic) strains.

METHODS

After conducting a systematic review, we meta-analyzed 31 case-control studies (N = 27,293) conducted between 2006 and 2020 using a random-effects regression model.

RESULTS

In high-income countries, RV1 VE was 10% lower against partially heterotypic (P = 0.04) and fully heterotypic (P = 0.10) compared with homotypic strains (homotypic VE: 90% [95% confidence intervals (CI): 82-94]; partially heterotypic VE: 79% [95% CI: 71-85]; fully heterotypic VE: 80% [95% CI: 65-88]). In middle-income countries, RV1 VE was 14-16% lower against partially heterotypic (P = 0.06) and fully heterotypic (P = 0.04) compared with homotypic strains (homotypic VE: 81% [95% CI: 69-88]; partially heterotypic VE: 67% [95% CI: 54-76]; fully heterotypic VE: 65% [95% CI: 51-75]). Strain-specific RV5 VE differences were less pronounced, and primarily derived from high-income countries. Limited data were available from low-income countries.

CONCLUSIONS

Vaccine effectiveness of RV1 and RV5 was somewhat lower against nonvaccine than vaccine strains. Ongoing surveillance is important to continue long-term monitoring for strain replacement, particularly in low-income settings where data are limited.

Association of Rotavirus Vaccines With Reduction in Rotavirus Gastroenteritis in Children Younger Than 5 Years: A Systematic Review and Meta-analysis of Randomized Clinical Trials and Observational Studies

IMPORTANCE

Rotavirus vaccines have been introduced worldwide, and the clinical association of different rotavirus vaccines with reduction in rotavirus gastroenteritis (RVGE) after introduction are noteworthy.

OBJECTIVE

To evaluate the comparative benefit, risk, and immunogenicity of different rotavirus vaccines by synthesizing randomized clinical trials (RCTs) and observational studies.

DATA SOURCES

Relevant studies published in 4 databases: Embase, PubMed, the Cochrane Library, and Web of Science were searched until July 1, 2020, using search terms including "rotavirus" and "vaccin*."

STUDY SELECTION

Randomized clinical trials and cohort and case-control studies involving more than 100 children younger than 5 years that reported the effectiveness, safety, or immunogenicity of rotavirus vaccines were included.

DATA EXTRACTION AND SYNTHESIS

A random-effects model was used to calculate relative risks (RRs), odds ratios (ORs), risk differences, and 95% CIs. Adjusted indirect treatment comparison was performed to assess the differences in the protection of Rotarix and RotaTeq.

MAIN OUTCOMES AND MEASURES

The primary outcomes were RVGE, severe RVGE, and RVGE hospitalization. Safety-associated outcomes involved serious adverse events, intussusception, and mortality.

RESULTS

A meta-analysis of 20 RCTs and 38 case-control studies revealed that Rotarix (RV1) significantly reduced RVGE (RR, 0.316 [95% CI, 0.224-0.345]) and RVGE hospitalization risk (OR, 0.347 [95% CI, 0.279-0.432]) among children fully vaccinated; RotaTeq (RV5) had similar outcomes (RVGE: RR, 0.350 [95% CI, 0.275-0.445]; RVGE hospitalization risk: OR, 0.272 [95% CI, 0.197-0.376]). Rotavirus vaccines also demonstrated higher protection against severe RVGE. Additionally, no significant differences in the protection of RV1 and RV5 against rotavirus disease were noted in adjusted indirect comparisons. Moderate associations were found between reduced RVGE risk and Rotavac (RR, 0.664 [95% CI, 0.548-0.804]), Rotasiil (RR, 0.705 [95% CI, 0.605-0.821]), and Lanzhou lamb rotavirus vaccine (RR, 0.407 [95% CI, 0.332-0.499]). All rotavirus vaccines demonstrated no risk of serious adverse events. A positive correlation was also found between immunogenicity and vaccine protection (eg, association of RVGE with RV1: coefficient, -1.599; adjusted R2, 99.7%).

CONCLUSIONS AND RELEVANCE

The high protection and low risk of serious adverse events for rotavirus vaccines in children who were fully vaccinated emphasized the importance of worldwide introduction of rotavirus vaccination. Similar protection provided by Rotarix and RotaTeq relieves the pressure of vaccines selection for health care authorities.

The impact of rotavirus vaccination in the prevalence of gastroenteritis and comorbidities among children after suboptimal rotavirus vaccines implementation in Taiwan: A population-based study

In Taiwan, rotavirus vaccination was implemented in 2006 in the private sector. The population-based impact of rotavirus vaccination on gastroenteritis and comorbidities of children remains under-investigated.We analyzed the annual prevalence of rotavirus-related disease, including gastroenteritis, convulsions, epilepsy, type I diabetes mellitus, intussusception, and biliary atresia among children under 5 years of age. Data were collected from Taiwan's National Health Insurance Research Database, a nationwide population-based database. A 16-year retrospective cohort study was conducted between 2000 and 2015.Among children <5 years of age, the prevalence of gastroenteritis decreased after 2012 (44,259.69 per 100 thousands) and remained lower through 2015 (39,931.11per 100 thousands, P < .001). The prevalence of convulsions rose steadily and significantly from 2007 (775.90 per 100 thousands) to 2015 (962.17 per 100 thousands, P < .001). The prevalence of epilepsy decreased significantly until reaching a nadir in 2013 (from 501.56 to 293.53 per 100 thousands, P < .001). The prevalence of biliary atresia tended upward, and surged suddenly in 2007 with a peak in 2013 (18.74 per 100 thousands). Among infants (<1 year of age) from 2000 to 2015, the prevalence of gastroenteritis declined steadily, and more rapidly after 2007 (22,513 to 17,285 per 100 thousands).In Taiwan, after introducing rotavirus vaccination, gastroenteritis in young children decreased, especially in infancy. However, gastroenteritis is still common in children, given other emerging pathogens. Our results highlight the impact of rotavirus vaccines on children's health in Taiwan and provide indications for future preventive medicine and healthcare strategies in children.

Thermostable, Dissolvable Buccal Film Rotavirus Vaccine Is Highly Effective in Neonatal Gnotobiotic Pig Challenge Model

Difficulties related to storage and transport of currently available live oral rotavirus vaccines can have detrimental consequences on the efficacy of the vaccines. Thus, there is a great need for thermostable vaccines that can eliminate the necessity for cold chain storage or reconstitution before administration. In this study, we developed a dissolvable oral polymeric film comprised of a live attenuated thermostable tetravalent rhesus-human reassortant rotavirus vaccine (RRV-TV) powder and antacid (CaCO3). Immunogenicity and protective efficacy of the vaccine after buccal delivery was evaluated in the gnotobiotic pig model of human rotavirus (HRV) infection and diarrhea. Two doses of the vaccine were highly immunogenic and conferred strong protection against virus shedding and diarrhea upon challenge with a high dose of a virulent G1 HRV in gnotobiotic pigs. Those pigs vaccinated with the preserved film vaccine had significantly delayed onset of diarrhea; reduced duration and area under the curve of diarrhea; delayed onset of fecal virus shedding; and reduced duration and peak of fecal virus shedding titers compared to pigs in both the placebo and the reconstituted liquid oral RRV-TV vaccine groups. Associated with the strong protection, high titers of serum virus neutralization antibodies against each of the four RRV-TV mono-reassortants and G1 HRV-specific serum IgA and IgG antibodies, as well as intestinal IgA antibodies, were induced by the preserved film vaccine. These results demonstrated the effectiveness of our thermostable buccal film rotavirus vaccine and warrant further investigation into the promise of the novel technology in addressing drawbacks of the current live oral HRV vaccines.

Effectiveness of the oral human attenuated pentavalent rotavirus vaccine (RotaTeq™) postlicensure: a meta-analysis-2006-2020

BACKGROUND

Rotavirus (RV), which causes RV-associated gastroenteritis (RVGE), has accounted for considerable morbidity. We aimed to assess the effectiveness (VE) of the oral pentavalent RV vaccine (RotaTeq™) in real-world settings in children and infants with gastroenteritis.

METHODS

We performed a systematic search for peer-reviewed studies published between 1 January 2006 and 1 May 2020 and a meta-analysis to calculate the VE of RotaTeq™ vaccine. The primary outcome was the pooled three-dose vaccine VE. Stratified analysis of the vaccine VEs was performed according to dosages, study design, population age, socioeconomic status (SES), introduction condition, control group types, outcomes of RV disease, and RV strains.

RESULTS

After screening 2359 unique records, 28 studies were included and meta-analyzed. The overall VE estimate was 84% (95% confidence interval [CI], 80-87%). Stratified analyses revealed a nonnegligible impact of factors such as study design and SES. Other factors did not show great impart to VE with no significant differences between groups.

CONCLUSIONS

RotaTeq™ is effective against RV infection, especially in high-income countries. Adopting suitable study methods and expansion of RV surveillance in low-income regions is crucial to assess VE in real-life settings and provide feasible vaccine regimens to improve vaccine VE.

Causal inference concepts applied to three observational studies in the context of vaccine development: from theory to practice

Background

Randomized controlled trials are considered the gold standard to evaluate causal associations, whereas assessing causality in observational studies is challenging.

Methods

We applied Hill’s Criteria, counterfactual reasoning, and causal diagrams to evaluate a potentially causal relationship between an exposure and outcome in three published observational studies: a) one burden of disease cohort study to determine the association between type 2 diabetes and herpes zoster, b) one post-authorization safety cohort study to assess the effect of AS04-HPV-16/18 vaccine on the risk of autoimmune diseases, and c) one matched case-control study to evaluate the effectiveness of a rotavirus vaccine in preventing hospitalization for rotavirus gastroenteritis.

Results

Among the 9 Hill’s criteria, 8 (Strength, Consistency, Specificity, Temporality, Plausibility, Coherence, Analogy, Experiment) were considered as met for study c, 3 (Temporality, Plausibility, Coherence) for study a, and 2 (Temporary, Plausibility) for study b. For counterfactual reasoning criteria, exchangeability, the most critical assumption, could not be tested. Using these tools, we concluded that causality was very unlikely in study b, unlikely in study a, and very likely in study c. Directed acyclic graphs provided complementary visual structures that identified confounding bias and helped determine the most accurate design and analysis to assess causality.

Conclusions

Based on our assessment we found causal Hill’s criteria and counterfactual thinking valuable in determining some level of certainty about causality in observational studies. Application of causal inference frameworks should be considered in designing and interpreting observational studies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12874-021-01220-1.

The impact of shared decision making with patient decision aids on the rotavirus vaccination rate in children: A randomized controlled trial

Rotavirus vaccination reduces the incidence and severity of acute gastroenteritis due to rotavirus infection. However, because of a lack of understanding and private payment for the rotavirus vaccine, the rotavirus vaccination rate is still low in some countries. We intended to assess the impact of shared decision-making (SDM) with the assistance of patient decision aids (PDAs) on the rotavirus vaccination rate, and the knowledge, confidence, and congruence of value among baby's parents when decision-making. The study was a two-group, outcome assessor-blind, randomized, controlled trial. The families of 1-month-old infants for routine vaccination were enrolled; they were divided randomly into non-SDM and SDM groups. The influence of SDM on the acceptance of rotavirus vaccination was assessed when their infants were 2 months old. Outcome measures were decisional conflict, decision-making difficulties, and rotavirus vaccine knowledge, and the overall rotavirus vaccination rate. The study enrolled 180 participants. SDM, parents' education level, and rotavirus vaccination of a previous child were variables that influenced acceptance of rotavirus vaccination. The SDM group scored significantly higher for understanding the information on the oral rotavirus vaccine than the non-SDM group, which helped them to decide whether to vaccinate the baby against rotavirus. The rotavirus vaccination rate was 16.7% higher in the SDM group than the non-SDM group. SDM assisted with PDAs gives more information and helps infants' families understand what they need, reduces their decision conflict, and increases their baby's vaccination against rotavirus, which promotes public health. The clinical trial is registered at ClinicalTrials.gov (NCT03804489).

Immune correlates analysis using vaccinees from test negative designs

Determining the effect of vaccine-induced immune response on disease risk is an important goal of vaccinology. Typically, immune correlates analyses are conducted prospectively with immune response measured shortly after vaccination and subsequent disease status regressed on immune response. In outbreaks and rare disease settings, collecting samples from all vaccinees is not feasible. The test negative design is a retrospective design used to measure vaccine efficacy where symptomatic individuals who present at a clinic are assessed for relevant disease (cases) or some other disease (controls) and vaccination status ascertained. This article proposes that test negative vaccinees have immune response to vaccine assessed both for relevant (e.g., Ebola) and irrelevant (e.g., vector) proteins. If the latter immune response is unaffected by active (Ebola) infection, and is correlated with the relevant immune response, it can serve as a proxy for the immune response of interest proximal to infection. We show that logistic regression using imputed immune response as the covariate and case disease as outcome can estimate the prospective immune response slope and detail the assumptions needed for unbiased inference. The method is evaluated by simulation under various scenarios including constant and decaying immune response. A simulated dataset motivated by ring vaccination for an ongoing Ebola outbreak is analyzed.

Overview of the Development, Impacts, and Challenges of Live-Attenuated Oral Rotavirus Vaccines

Safety, efficacy, and cost-effectiveness are paramount to vaccine development. Following the isolation of rotavirus particles in 1969 and its evidence as an aetiology of severe dehydrating diarrhoea in infants and young children worldwide, the quest to find not only an acceptable and reliable but cost-effective vaccine has continued until now. Four live-attenuated oral rotavirus vaccines (LAORoVs) (Rotarix^®, RotaTeq^®, Rotavac^®, and RotaSIIL^®) have been developed and licensed to be used against all forms of rotavirus-associated infection. The efficacy of these vaccines is more obvious in the high-income countries (HIC) compared with the low- to middle-income countries (LMICs); however, the impact is far exceeding in the low-income countries (LICs). Despite the rotavirus vaccine efficacy and effectiveness, more than 90 countries (mostly Asia, America, and Europe) are yet to implement any of these vaccines. Implementation of these vaccines has continued to suffer a setback in these countries due to the vaccine cost, policy, discharging of strategic preventive measures, and infrastructures. This review reappraises the impacts and effectiveness of the current live-attenuated oral rotavirus vaccines from many representative countries of the globe. It examines the problems associated with the low efficacy of these vaccines and the way forward. Lastly, forefront efforts put forward to develop initial procedures for oral rotavirus vaccines were examined and re-connected to today vaccines.

Evaluating Partial Series Childhood Vaccination Services in a Mobile Clinic Setting

This study aims to evaluate the cost-benefit of vaccination services, mostly partial series administration, provided by a mobile clinic program (MCP) in Houston for children of transient and low-income families. The study included 469 patients who visited the mobile clinics on regular service days in 2 study periods in 2014 and 836 patients who attended vaccination events in the summer of 2014. The benefit of partial series vaccination was estimated based on vaccine efficacy/effectiveness data. Our conservative cost-benefit estimates show that, compared with office-based settings, every dollar spent on vaccination by the MCP would result in $0.9 societal cost averted as an incremental benefit in regular service days and $3.7 during vaccination-only events. To further improve the cost-benefit of vaccination services in the MCP, decision-makers and stakeholders may consider improving work efficiency during regular service days or hosting more vaccination events.

Divergence of group a rotavirus with genetic variations before and after introduction of rotavirus vaccines in northern Taiwan

Despite the development of vaccines in 2006, rotavirus is still a major cause of acute gastroenteritis worldwide. This study was performed to analyze the presence of circulating rotaviruses before and after the introduction of rotavirus vaccines to allow phylogenetic comparisons of vaccine strains in northern Taiwan.Rotavirus genotyping and sequencing of rotavirus VP7 and VP4 PCR products were performed by Reverse Transcriptase Polymerase Chain Reaction and DNA autosequencing. Phylogenies were constructed by the neighbor-joining and maximum-likelihood methods using CLUSTAL W software included in the MEGA software package (version 6.0).Between April 2004 and December 2012, a total of 101 rotavirus specimens from pediatric patients with acute gastroenteritis hospitalized in Chang Gung Children's Hospital were amplified, and their VP4 and VP7 sequences were determined. These 101 specimens consisted of 55 pre-vaccine strains (G1 [13, 23.6%], G2 [12, 21.8%], G3 [16, 29.1%], and G9 [14, 25.5%]) and 46 post-vaccine strains (G1 [25, 54.3%], G2 [12, 26.1%], G3 [5, 10.9%], and G9 [4, 8.7%]). The most common combination of the G and P types was G2P[4], accounting for 36% cases, followed by G9P[8] (25%), G1P[8] (20%), G3P[4] (15%), G3P[8] (10%), G1P[4] (5%), and G2P[8] (5%). Phylogenetic analysis showed that only the G1 and P[8] genotypes clustered in the same lineages with the rotavirus vaccine strains.Based on our results, the inclusion of G9, modified G2 and G3 with target lineages, and the combination G2P[4] and G9P[8] in the rotavirus vaccines in Taiwan is warranted as a vaccination strategy.

Mucosal delivery of tuberculosis vaccines: a review of current approaches and challenges

Introduction: Tuberculosis (TB) remains a major health threat and it is now clear that the current vaccine, BCG, is unable to arrest the global TB epidemic. A new vaccine is needed to either replace or boost BCG so that a better level of protection could be achieved. The route of entry of Mycobacterium tuberculosis, the causative organism, is via inhalation making TB primarily a respiratory disease. There is therefore good reason to hypothesize that a mucosally delivered vaccine against TB could be more effective than one delivered via the systemic route.

Areas covered: This review summarizes the progress that has been made in the area of TB mucosal vaccines in the last few years. It highlights some of the strengths and shortcomings of the published evidence and aims to discuss immunological and practical considerations in the development of mucosal vaccines.

Expert opinion: There is a growing body of evidence that the mucosal approach to vaccination against TB is feasible and should be pursued. However, further key studies are necessary to both improve our understanding of the protective immune mechanisms operating in the mucosa and the technical aspects of aerosolized delivery, before such a vaccine could become a feasible, deployable strategy.

Parenterally Administered P24-VP8* Nanoparticle Vaccine Conferred Strong Protection against Rotavirus Diarrhea and Virus Shedding in Gnotobiotic Pigs

Current live rotavirus vaccines are costly with increased risk of intussusception due to vaccine replication in the gut of vaccinated children. New vaccines with improved safety and cost-effectiveness are needed. In this study, we assessed the immunogenicity and protective efficacy of a novel P24-VP8* nanoparticle vaccine using the gnotobiotic (Gn) pig model of human rotavirus infection and disease. Three doses of P24-VP8* (200 μg/dose) intramuscular vaccine with Al(OH)₃ adjuvant (600 μg) conferred significant protection against infection and diarrhea after challenge with virulent Wa strain rotavirus. This was indicated by the significant reduction in the mean duration of diarrhea, virus shedding in feces, and significantly lower fecal cumulative consistency scores in post-challenge day (PCD) 1-7 among vaccinated pigs compared to the mock immunized controls. The P24-VP8* vaccine was highly immunogenic in Gn pigs. It induced strong VP8*-specific serum IgG and Wa-specific virus-neutralizing antibody responses from post-inoculation day 21 to PCD 7, but did not induce serum or intestinal IgA antibody responses or a strong effector T cell response, which are consistent with the immunization route, the adjuvant used, and the nature of the non-replicating vaccine. The findings are highly translatable and thus will facilitate clinical trials of the P24-VP8* nanoparticle vaccine.

Challenges in estimating influenza vaccine effectiveness

Introduction: Influenza vaccination is regarded as the most effective way to prevent influenza infection. Due to the rapid genetic changes that influenza viruses undergo, seasonal influenza vaccines must be reformulated and re-administered annually necessitating the evaluation of influenza vaccine effectiveness (VE) each year. The estimation of influenza VE presents numerous challenges. Areas Covered: This review aims to identify, discuss, and, where possible, offer suggestions for dealing with the following challenges in estimating influenza VE: different outcomes of interest against which VE is estimated, study designs used to assess VE, sources of bias and confounding, repeat vaccination, waning immunity, population level effects of vaccination, and VE in at-risk populations. Expert Opinion: The estimation of influenza VE has improved with surveillance networks, better understanding of sources of bias and confounding, and the implementation of advanced statistical methods. Future research should focus on better estimates of the indirect effects of vaccination, the biological effects of vaccination, and how vaccines interact with the immune system. Specifically, little is known about how influenza vaccination impacts an individual's infectiousness, how vaccines wane over time, and the impact of repeated vaccination.

Enterovirus A71 vaccine effectiveness in preventing enterovirus A71 infection among medically-attended hand, foot, and mouth disease cases, Beijing, China

Introduction: Enterovirus A71(EV-A71)-associated hand, foot, and mouth disease (HFMD) has been reported worldwide, and poses a particularly heavy burden on patients, families, and society in China. Three Chinese companies have licensed inactivated EV-A71 vaccines, all of which have demonstrated good efficacy for preventing EV-A71-associated disease in clinical trials. However, real-world performance of EV-A71 vaccine has not been evaluated.

Methods: We used a test-negative design case-control study to estimate vaccine effectiveness (VE) against medically attended EV-A71-associated HFMD. Subjects were children 5 years of age and under who had been in health facilities participating in the HFMD case and virologic surveillance platforms in Beijing. Enterovirus infections were laboratory confirmed, and EV-A71 vaccination status was extracted from electronic immunization records. Children testing positive for EV-A71 were cases; controls were children testing negative for EV-A71 infection. Logistic regression was used to estimate VE. We assessed sensitivity of VE estimates to control group inclusion criteria by repeating the regression analyses with two alternative control groups.

Results: A total of 2,184 HFMD patients aged 5 years and under were enrolled in the study; 24 were severe, and 2,160 were mild. For severe cases, two-dose VE estimate was 100% (95% CI: −68.1%, 100%). For mild cases, 1-dose and 2-dose adjusted VE estimates were 69.8% and 83.7%, respectively. Two-dose VE estimates varied by less than 4 percentage points regardless of control group definition.

Conclusions: Our findings suggested the vaccines performed well in the real world for children 5 years of age and under in Beijing, China.

Measurement of Vaccine Direct Effects Under the Test-Negative Design

Test-negative designs are commonplace in assessments of influenza vaccination effectiveness, estimating this value from the exposure odds ratio of vaccination among individuals treated for acute respiratory illness who test positive for influenza virus infection. This approach is widely believed to recover the vaccine direct effect by correcting for differential health-care-seeking behavior among vaccinated and unvaccinated persons. However, the relationship of the measured odds ratio to true vaccine effectiveness is poorly understood. We derived the odds ratio under circumstances of real-world test-negative studies. The odds ratio recovers the vaccine direct effect when 2 conditions are met: 1) Individuals' vaccination decisions are uncorrelated with exposure or susceptibility to the test-positive or test-negative conditions, and 2) vaccination confers "all-or-nothing" protection (whereby certain individuals have no protection while others are perfectly protected). Biased effect-size estimates arise if either condition is unmet. Such bias might suggest misleading associations of vaccine effectiveness with time since vaccination or the force of infection of influenza. The test-negative design could also fail to correct for differential health-care-seeking behavior among vaccinated and unvaccinated persons without stringent criteria for enrollment and testing. Our findings demonstrate a need to reassess how data from test-negative studies can inform policy decisions.

Gamma-irradiated rotavirus: A possible whole virus inactivated vaccine

Rotavirus (RV) causes significant morbidity and mortality in developing countries, where children and infants are highly susceptible to severe disease symptoms. While live attenuated vaccines are available, reduced vaccine efficacy in developing countries illustrates the need for highly immunogenic alternative vaccines. Here, we studied the possible inactivation of RV using gamma(γ)-irradiation, and assessed the sterility and immunogenicity of γ-irradiated RV (γ-RV) as a novel vaccine candidate. Interestingly, the inactivation curve of RV did not show a log-linear regression following exposure to increased doses of γ-rays, and consequently the radiation dose required to achieve the internationally accepted Sterility Assurance Level could not be calculated. Nonetheless, we performed sterility testing based on serial passages of γ-RV, and our data clearly illustrate the lack of infectivity of γ-RV preparations irradiated with 50 kGy. In addition, we tested the immunogenicity of 50 kGy γ-RV in mice and our data illustrate the induction of strong RV-specific neutralising antibody responses following administration of γ-RV without using adjuvant. Therefore, whilst γ-RV may not constitute a replacement for current RV vaccines, this study represents a proof-of-concept that γ-irradiation can be applied to inactivate RV for vaccine purposes. Further investigation will be required to address whether γ-irradiation can be applied to improve safety and efficacy of existing live attenuated vaccines.

Effectiveness of Rotavirus Vaccination: A Systematic Review of the First Decade of Global Postlicensure Data, 2006-2016

Two rotavirus vaccines, Rotarix (RV1) and RotaTeq (RV5), were licensed for global use in 2006. A systematic review of 48 peer- reviewed articles with postlicensure data from 24 countries showed a median RV1 vaccine effectiveness (VE) of 84%, 75%, and 57% in countries with low, medium, and high child mortality, respectively, and RV5 VE of 90% and 45% in countries with low and high child mortality, respectively. A partial vaccine series provided considerable protection, but not to the same level as a full series. VE tended to decline in the second year of life, particularly in medium- and high-mortality settings, and tended to be greater against more severe rotavirus disease. Postlicensure data from countries across geographic regions and with different child mortality levels demonstrate that under routine use, both RV1 and RV5 are effective against rotavirus disease, supporting the World Health Organization recommendation that all countries introduce rotavirus vaccine into their national immunization program.

Rotavirus vaccines: why continued investment in research is necessary

PURPOSE OF REVIEW

Rotavirus vaccines were first introduced more than a decade ago and have had a tremendous impact on reducing the number of hospitalizations and deaths due to rotavirus-associated diarrhea. This review will discuss current rotavirus vaccines, post-licensure surveillance, progress in non-replicating vaccine development, and why continued research is important for understanding a virus that remains a globally leading cause of death due to diarrhea.

RECENT FINDINGS

Research advances have enhanced our understanding of how vaccines induce protection against subsequent severe disease, how the virus replicates and spreads in the face of the host immune system, and basic mechanisms governing the viral life cycle.

SUMMARY

Much remains to be learned about how to improve vaccine success, what are the molecular determinants of host range and virulence, and what are the interactions of the virus with the host that drive its replicative success, among many other important questions.

Correlates of protection for enteric vaccines

An immunological Correlate of Protection (CoP) is an immune response that is statistically interrelated with protection. Identification of CoPs for enteric vaccines would help design studies to improve vaccine performance of licensed vaccines in low income settings, and would facilitate the testing of future vaccines in development that might be more affordable. CoPs are lacking today for most existing and investigational enteric vaccines. In order to share the latest information on CoPs for enteric vaccines and to discuss novel approaches to correlate mucosal immune responses in humans with protection, the Foundation Mérieux organized an international conference of experts where potential CoPs for vaccines were examined using case-studies for both bacterial and viral enteric pathogens. Experts on the panel concluded that to date, all established enteric vaccine CoPs, such as those for hepatitis A, Vi typhoid and poliovirus vaccines, are based on serological immune responses even though these may poorly reflect the relevant gut immune responses or predict protective efficacy. Known CoPs for cholera, norovirus and rotavirus could be considered as acceptable for comparisons of similarly composed vaccines while more work is still needed to establish CoPs for the remaining enteric pathogens and their candidate vaccines. Novel approaches to correlate human mucosal immune responses with protection include the investigation of gut-originating antibody-secreting cells (ASCs), B memory cells and follicular helper T cells from samples of peripheral blood during their recirculation.

Case-control vaccine effectiveness studies: Data collection, analysis and reporting results

The case-control methodology is frequently used to evaluate vaccine effectiveness post-licensure. The results of such studies provide important insight into the level of protection afforded by vaccines in a 'real world' context, and are commonly used to guide vaccine policy decisions. However, the potential for bias and confounding are important limitations to this method, and the results of a poorly conducted or incorrectly interpreted case-control study can mislead policies. In 2012, a group of experts met to review recent experience with case-control studies evaluating vaccine effectiveness; we summarize the recommendations of that group regarding best practices for data collection, analysis, and presentation of the results of case-control vaccine effectiveness studies. Vaccination status is the primary exposure of interest, but can be challenging to assess accurately and with minimal bias. Investigators should understand factors associated with vaccination as well as the availability of documented vaccination status in the study context; case-control studies may not be a valid method for evaluating vaccine effectiveness in settings where many children lack a documented immunization history. To avoid bias, it is essential to use the same methods and effort gathering vaccination data from cases and controls. Variables that may confound the association between illness and vaccination are also important to capture as completely as possible, and where relevant, adjust for in the analysis according to the analytic plan. In presenting results from case-control vaccine effectiveness studies, investigators should describe enrollment among eligible cases and controls as well as the proportion with no documented vaccine history. Emphasis should be placed on confidence intervals, rather than point estimates, of vaccine effectiveness. Case-control studies are a useful approach for evaluating vaccine effectiveness; however careful attention must be paid to the collection, analysis and presentation of the data in order to best inform evidence-based vaccine policies.

Case-control vaccine effectiveness studies: Preparation, design, and enrollment of cases and controls

Case-control studies are commonly used to evaluate effectiveness of licensed vaccines after deployment in public health programs. Such studies can provide policy-relevant data on vaccine performance under ‘real world’ conditions, contributing to the evidence base to support and sustain introduction of new vaccines. However, case-control studies do not measure the impact of vaccine introduction on disease at a population level, and are subject to bias and confounding, which may lead to inaccurate results that can misinform policy decisions. In 2012, a group of experts met to review recent experience with case-control studies evaluating the effectiveness of several vaccines; here we summarize the recommendations of that group regarding best practices for planning, design and enrollment of cases and controls. Rigorous planning and preparation should focus on understanding the study context including healthcare-seeking and vaccination practices. Case-control vaccine effectiveness studies are best carried out soon after vaccine introduction because high coverage creates strong potential for confounding. Endpoints specific to the vaccine target are preferable to non-specific clinical syndromes since the proportion of non-specific outcomes preventable through vaccination may vary over time and place, leading to potentially confusing results. Controls should be representative of the source population from which cases arise, and are generally recruited from the community or health facilities where cases are enrolled. Matching of controls to cases for potential confounding factors is commonly used, although should be reserved for a limited number of key variables believed to be linked to both vaccination and disease. Case-control vaccine effectiveness studies can provide information useful to guide policy decisions and vaccine development, however rigorous preparation and design is essential.

Use of Patients With Diarrhea Who Test Negative for Rotavirus as Controls to Estimate Rotavirus Vaccine Effectiveness Through Case-Control Studies

BACKGROUND

Case-control studies are often performed to estimate postlicensure vaccine effectiveness (VE), but the enrollment of controls can be challenging, time-consuming, and costly. We evaluated whether children enrolled in the same hospital-based diarrheal surveillance used to identify rotavirus cases but who test negative for rotavirus (test-negative controls) can be considered a suitable alternative to nondiarrheal hospital or community-based control groups (traditional controls).

METHODS

We compared calculated VE estimates as a function of varying values of true VE, attack rates of rotavirus and nonrotavirus diarrhea in the population, and sensitivity and specificity of the rotavirus enzyme immunoasssay. We also searched the literature to identify rotavirus VE studies that used traditional and test-negative control groups and compared VE estimates obtained using the different control groups.

RESULTS

Assuming a 1% attack rate for severe rotavirus diarrhea, a 3% attack rate for severe nonrotavirus diarrhea in the population, a test sensitivity of 96%, and a specificity of 100%, the calculated VE estimates using both the traditional and test-negative control groups closely approximated the true VE for all values from 30% to 100%. As true VE decreased, the traditional case-control approach slightly overestimated the true VE and the test-negative case-control approach slightly underestimated this estimate, but the absolute difference was only ±0.2 percentage points. Field VE estimates from 10 evaluations that used both traditional and test-negative control groups were similar regardless of control group used.

CONCLUSIONS

The use of rotavirus test-negative controls offers an efficient and cost-effective approach to estimating rotavirus VE through case-control studies.

Immunization information systems to increase vaccination rates: a community guide systematic review

CONTEXT

Immunizations are the most effective way to reduce incidence of vaccine-preventable diseases. Immunization information systems (IISs) are confidential, population-based, computerized databases that record all vaccination doses administered by participating providers to people residing within a given geopolitical area. They facilitate consolidation of vaccination histories for use by health care providers in determining appropriate client vaccinations. Immunization information systems also provide aggregate data on immunizations for use in monitoring coverage and program operations and to guide public health action.

EVIDENCE ACQUISITION

Methods for conducting systematic reviews for the Guide to Community Preventive Services were used to assess the effectiveness of IISs. Reviewed evidence examined changes in vaccination rates in client populations or described expanded IIS capabilities related to improving vaccinations. The literature search identified 108 published articles and 132 conference abstracts describing or evaluating the use of IISs in different assessment categories.

EVIDENCE SYNTHESIS

Studies described or evaluated IIS capabilities to (1) create or support effective interventions to increase vaccination rates, such as client reminder and recall, provider assessment and feedback, and provider reminders; (2) determine client vaccination status to inform decisions by clinicians, health care systems, and schools; (3) guide public health responses to outbreaks of vaccine-preventable disease; (4) inform assessments of vaccination coverage, missed vaccination opportunities, invalid dose administration, and disparities; and (5) facilitate vaccine management and accountability.

CONCLUSIONS

Findings from 240 articles and abstracts demonstrate IIS capabilities and actions in increasing vaccination rates with the goal of reducing vaccine-preventable disease.

Bias with respect to socioeconomic status: A closer look at zip code matching in a pneumococcal vaccine effectiveness study

In 2010, 13-valent pneumococcal conjugate vaccine (PCV13) was introduced in the US for prevention of invasive pneumococcal disease in children. Individual-level socioeconomic status (SES) is a potential confounder of the estimated effectiveness of PCV13 and is often controlled for in observational studies using zip code as a proxy. We assessed the utility of zip code matching for control of SES in a post-licensure evaluation of the effectiveness of PCV13 (calculated as [1-matched odds ratio]*100). We used a directed acyclic graph to identify subsets of confounders and collected SES variables from birth certificates, geocoding, a parent interview, and follow-up with medical providers. Cases tended to be more affluent than eligible controls (for example, 48.3% of cases had private insurance vs. 44.6% of eligible controls), but less affluent than enrolled controls (52.9% of whom had private insurance). Control of confounding subsets, however, did not result in a meaningful change in estimated vaccine effectiveness (original estimate: 85.1%, 95% CI 74.8–91.9%; adjusted estimate: 82.5%, 95% CI 65.6–91.1%). In the context of a post-licensure vaccine effectiveness study, zip code appears to be an adequate, though not perfect, proxy for individual SES.

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Socioeconomic status (SES) may impact enrollment in vaccine effectiveness studies.

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We assessed zip code matching as a proxy for SES in a pneumococcal vaccine study.

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After zip code matching, we found differences in SES between cases and controls.

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Differences did not appear to substantially bias estimated vaccine effectiveness.

Effectiveness of rotavirus vaccine in preventing severe gastroenteritis in young children according to socioeconomic status

In 2011, the monovalent rotavirus vaccine was introduced into a universal immunization program in Quebec (Canada). This retrospective cohort study assessed vaccine effectiveness (VE) in preventing acute gastroenteritis (AGE) and rotavirus gastroenteritis (RVGE) hospitalizations among children <3 y living in the Quebec Eastern Townships region according to socioeconomic status (SES). Data were gathered from a tertiary hospital database paired with a regional immunization registry. Three cohorts of children were followed: (1) vaccinated children born in post-universal vaccination period (2011-2013, n = 5,033), (2) unvaccinated children born in post-universal vaccination period (n = 1,239), and (3) unvaccinated children born in pre-universal vaccination period (2008-2010, n = 6,436). In each cohort, AGE and RVGE hospitalizations were identified during equivalent follow-up periods to calculate VE globally and according to neighborhood-level SES. Using multivariable logistic regression, adjusted odds ratios (OR) were computed to obtain VE (1-OR). Adjusted VE of 2 doses was 62% (95% confidence interval [CI]: 37%-77%) and 94% (95%CI: 52%-99%) in preventing AGE and RVGE hospitalization, respectively. Stratified analyses according to SES showed that children living in neighborhoods with higher rates of low-income families had significantly lower VE against AGE hospitalizations compared to neighborhoods with lower rates of low-income families (30% vs. 78%, p = 0.027). Our results suggest that the rotavirus vaccine is highly effective in preventing severe gastroenteritis in young children, particularly among the most well-off. SES seems to influence rotavirus VE, even in a high-income country like Canada. Further studies are needed to determine factors related to lower rotavirus VE among socioeconomically disadvantaged groups.

Rotavirus vaccine effectiveness in Hong Kong children

BACKGROUND

Rotavirus is a common infectious cause of childhood hospitalisation in Hong Kong. Rotavirus vaccines have been used in the private sector since licensure in 2006 but have not been incorporated in the government's universal Childhood Immunisation Programme. This study aimed to evaluate rotavirus vaccine effectiveness against hospitalisation.

METHODS

This case-control study was conducted in the 2014/2015 rotavirus season in six public hospitals. Hospitalised acute gastroenteritis patients meeting inclusion criteria were recruited and copies of their immunisation records were collected. Case-patients were defined as enrolled subjects with stool specimens obtained in the first 48h of hospitalisation that tested positive for rotavirus, whereas control-patients were those with stool specimens obtained in the first 48h of hospitalisation testing negative for rotavirus. Vaccine effectiveness for administration of at least one dose of either Rotarix(®) (GlaxoSmithKline Biologicals) or RotaTeq(®) (Merck Research Laboratories) was calculated as 1 minus the odds ratio for rotavirus vaccination history for case-patients versus control-patients.

RESULTS

Among the 525 eligible subjects recruited, immunisation records were seen in 404 (77%) subjects. 31% (162/525 and 126/404) tested positive for rotavirus. In the 404 subjects assessed for vaccine effectiveness, 2.4% and 24% received at least 1 dose of either rotavirus vaccine in case- and control-patients respectively. The unmatched vaccine effectiveness against hospitalisation for administration of at least one dose of either rotavirus vaccines was 92% (95% confidence interval [CI]: 75%, 98%). The matched analyses by age only and both age and admission date showed 96% (95% CI: 72%, 100%) and 89% (95% CI: 51%, 97%) protection against rotavirus hospitalisation respectively.

CONCLUSIONS

Rotavirus vaccine is highly effective in preventing hospitalisation from rotavirus disease in young Hong Kong children.

Rotavirus Surveillance at a WHO-Coordinated Invasive Bacterial Disease Surveillance Site in Bangladesh: A Feasibility Study to Integrate Two Surveillance Systems

The World Health Organization (WHO) currently coordinates rotavirus diarrhea and invasive bacterial disease (IBD) surveillance at 178 sentinel sites in 60 countries. However, only 78 sites participate in both surveillance systems using a common sentinel site. Here, we explored the feasibility of extending a WHO-IBD surveillance platform to generate data on the burden of rotaviral diarrhea and its epidemiological characteristics to prepare the countries to measure the impact of rotaviral vaccine. A six-month (July to December, 2012) surveillance, managed by IBD team, collected stool samples and clinical data from under-five children with acute watery diarrhea at an IBD sentinel site. Samples were tested for rotavirus antigen by ELISA and genotyped by PCR at the regional reference laboratory (RRL). Specimens were collected from 79% (n = 297) of eligible cases (n = 375); 100% of which were tested for rotavirus by ELISA and 54% (159/297) of them were positive. At RRL, all the cases were confirmed by PCR and genotyped (99%; 158/159). The typing results revealed the predominance of G12 (40%; 64/159) genotype, followed by G1 (31%; 50/159) and G9 (19%; 31/159). All in all, this exploratory surveillance collected the desired demographic and epidemiological data and achieved almost all the benchmark indicators of WHO, starting from enrollment number to quality assurance through a number of case detection, collection, and testing of specimens and genotyping of strains at RRL. The success of this WHO-IBD site in achieving these benchmark indicators of WHO can be used by WHO as a proof-of-concept for considering integration of rotavirus surveillance with WHO-IBD platforms, specifically in countries with well performing IBD site and no ongoing rotavirus surveillance.

Impact of vaccination uptake on hospitalizations due to rotavirus acute gastroenteritis in 2 different socioeconomic areas of Spain

Rotavirus is the leading cause of hospitalization due to acute gastroenteritis (AGE) in infants and toddlers. However, rotavirus vaccination has been associated with a decline in hospitalization rates due to rotavirus AGE. A descriptive retrospective study was conducted to analyze the impact of rotavirus vaccination on the rate of hospitalizations due to AGE among children ≤2 years old in 2 areas of the province of Almería, Spain. After eight years of rotavirus vaccination, rates of hospitalizations due to rotavirus AGE are diminished. This decline is closely related to vaccine coverage in the studied areas.

Beyond efficacy: The full public health impact of vaccines

There is an active discussion in the public health community on how to assess and incorporate, in addition to safety and measures of protective efficacy, the full public health value of preventive vaccines into the evidence-based decision-making process of vaccine licensure and recommendations for public health use. The conference "Beyond efficacy: the full public health impact of vaccines in addition to efficacy measures in trials" held in Annecy, France (June 22-24, 2015) has addressed this issue and provided recommendations on how to better capture the whole public health impact of vaccines. Using key examples, the expert group stressed that we are in the midst of a new paradigm in vaccine evaluation, where all aspects of public health value of vaccines beyond efficacy should be evaluated. To yield a wider scope of vaccine benefits, additional measures such as vaccine preventable disease incidence, overall efficacy and other outcomes such as under-five mortality or non-etiologically confirmed clinical syndromes should be assessed in addition to traditional efficacy or effectiveness measurements. Dynamic modelling and the use of probe studies should also be considered to provide additional insight to the full public health value of a vaccine. The use of burden reduction and conditional licensure of vaccines based on collection of outcome results should be considered by regulatory agencies.

Cost-effectiveness of rotavirus vaccination in Kenya and Uganda

INTRODUCTION

Rotavirus vaccines have the potential to prevent a substantial amount of life-threatening gastroenteritis in young African children. This paper presents the results of prospective cost-effectiveness analyses for rotavirus vaccine introduction for Kenya and Uganda.

METHODOLOGY

In each country, a national consultant worked with a national technical working group to identify appropriate data and validate study results. Secondary data on demographics, disease burden, health utilization, and costs were used to populate the TRIVAC cost-effectiveness model. The baseline analysis assumed an initial vaccine price of $0.20 per dose, corresponding to Gavi, the Vaccine Alliance stipulated copay for low-income countries. The incremental cost-effectiveness of a 2-dose rotavirus vaccination schedule was evaluated for 20 successive birth cohorts from the government perspective in both countries, and from the societal perspective in Uganda.

RESULTS

Between 2014 and 2033, rotavirus vaccination can avert approximately 60,935 and 216,454 undiscounted deaths and hospital admissions respectively in children under 5 years in Kenya. In Uganda, the respective number of undiscounted deaths and hospital admission averted is 70,236 and 329,779 between 2016 and 2035. Over the 20-year period, the discounted vaccine program costs are around US$ 80 million in Kenya and US$ 60 million in Uganda. Discounted government health service costs avoided are US$ 30 million in Kenya and US$ 10 million in Uganda (or US$ 18 million including household costs). The cost per disability-adjusted life-year (DALY) averted from a government perspective is US$ 38 in Kenya and US$ 34 in Uganda (US$ 29 from a societal perspective).

CONCLUSIONS

Rotavirus vaccine introduction is highly cost-effective in both countries in a range of plausible 'what-if' scenarios. The involvement of national experts improves the quality of data used, is likely to increase acceptability of the results in decision-making, and can contribute to strengthened national capacity to undertake economic evaluations.

Impact of a publicly funded monovalent rotavirus vaccination program in the Province of Quebec (Canada)

In November 2011, the province of Quebec, Canada implemented a publicly funded rotavirus (RV) vaccination program using the monovalent RV vaccine (RV1). To assess its impact, trends in passive RV laboratory detection and Emergency Department (ED) visits for gastroenteritis (GE) at two pediatric centers were evaluated.

METHODS

RV tests performed were extracted from the virology laboratory databases and ED visits for GE between July 1, 2006 and June 30, 2013, from the ED databases of The Montreal Children's Hospital (MCH) and Centre Hospitalier Universitaire de Sherbrooke (CHUS). The percent positive RV tests over time and season duration were assessed using 5-week moving averages. We defined season start and end as the first two and the last two consecutive weeks where the percent positive RV tests were ≥ 10%, respectively.

RESULTS

Comparing the pre- and post-vaccination program periods, a decrease in the proportion of positive RV tests was seen: 15.9% vs. 5.1% (p<0.001). Pre-vaccination program, RV seasons started between December and February, peaked in March or April and ended in May. In 2011-2012, the season started in March, peaked in April, and ended in May. In 2012-2013, the season lasted 3 weeks in May. ED visits for GE decreased post-introduction of the RV1 program: from 4.8% to 3.4% in 2011-2012, and 4.2% in 2012-13 (p<0.001). In children <2 years of age, ED GE visits decreased from 7.5% to 4.8% in 2011-2012, and 5.2% in 2012-2013 (p<0.001). Admissions for GE also decreased significantly from 0.41% of all ED visits to 0.14% in 2011-2012 and 0.22% in 2012-2013 (p<0.005).

CONCLUSION

Implementation of a publicly funded RV vaccination program had a major impact on the epidemiology of RV infections in Quebec: RV seasons have started later and been of shorter duration, peak positives were fewer, and ED visits for GE decreased.

Public Health Impact of Complete and Incomplete Rotavirus Vaccination among Commercially and Medicaid Insured Children in the United States

Background

This study (NCT01682005) aims to assess clinical and cost impacts of complete and incomplete rotavirus (RV) vaccination.

Methods

Beneficiaries who continuously received medical and pharmacy benefits since birth were identified separately in Truven Commercial Claims and Encounters (2000–2011) and Truven Medicaid Claims (2002–2010) and observed until the first of end of insurance eligibility or five years. Infants with ≥1 RV vaccine within the vaccination window (6 weeks-8 months) were divided into completely and incompletely vaccinated cohorts. Historically unvaccinated (before 2007) and contemporarily unvaccinated (2007 and after) cohorts included children without RV vaccine. Claims with International Classification of Disease 9^th edition (ICD-9) codes for diarrhea and RV were identified. First RV episode incidence, RV-related and diarrhea-related healthcare resource utilization after 8 months old were calculated and compared across groups. Poisson regressions were used to generate incidence rates with 95% confidence intervals (CIs). Mean total, inpatient, outpatient and emergency room costs for first RV and diarrhea episodes were calculated; bootstrapping was used to construct 95% CIs to evaluate cost differences.

Results

1,069,485 Commercial and 515,557 Medicaid patients met inclusion criteria. Among commercially insured, RV incidence per 10,000 person-years was 3.3 (95% CI 2.8–3.9) for completely, 4.0 (95% CI 3.3–5.0) for incompletely vaccinated, and 20.9 (95% CI 19.5–22.4) for contemporarily and 40.3 (95% CI 38.6–42.1) for historically unvaccinated. Rates in Medicaid were 7.5 (95% CI 4.8–11.8) for completely, 9.0 (95% CI 6.5–12.3) for incompletely vaccinated, and 14.6 (95% CI 12.8–16.7) for contemporarily and 52.0 (95% CI 50.2–53.8) for historically unvaccinated. Mean cost for first RV episode per cohort member was $15.33 (95% CI $12.99-$18.03) and $4.26 ($95% CI $2.34-$6.35) lower for completely vaccinated versus contemporarily unvaccinated in Commercial and Medicaid, respectively.

Conclusions

RV vaccination results in significant reduction in RV infection. There is evidence of indirect benefit to unvaccinated individuals.

Epidemiologic Association Between FUT2 Secretor Status and Severe Rotavirus Gastroenteritis in Children in the United States

IMPORTANCE

A genetic polymorphism affecting FUT2 secretor status in approximately one-quarter of humans of European descent affects the expression of histo-blood group antigens on the mucosal epithelia of human respiratory, genitourinary, and digestive tracts. These histo-blood group antigens serve as host receptor sites necessary for attachment and infection of some pathogens, including norovirus.

OBJECTIVE

We investigated whether an association exists between FUT2 secretor status and laboratory-confirmed rotavirus infections in US children.

DESIGN, SETTING, AND PARTICIPANTS

Multicenter case-control observational study involving active surveillance at 6 US pediatric medical institutions in the inpatient and emergency department clinical settings. We enrolled 1564 children younger than 5 years with acute gastroenteritis (diarrhea and/or vomiting) and 818 healthy controls frequency matched by age and month, from December 1, 2011, through March 31, 2013.

MAIN OUTCOMES AND MEASURES

Paired fecal-saliva specimens were tested for rotavirus and for secretor status. Comparisons were made between rotavirus test-positive cases and healthy controls stratified by ethnicity and vaccination status. Adjusted multivariable analyses assessed the preventive association of secretor status against severe rotavirus gastroenteritis.

RESULTS

One (0.5%) of 189 rotavirus test-positive cases was a nonsecretor, compared with 188 (23%) of 818 healthy control participants (P < .001). Healthy control participants of Hispanic ethnicity were significantly less likely to be nonsecretors (13%) compared with healthy children who were not of Hispanic ethnicity (25%) (P < .001). After controlling for vaccination and other factors, children with the nonsecretor FUT2 polymorphism appeared statistically protected (98% [95% CI, 84%-100%]) against severe rotavirus gastroenteritis.

CONCLUSIONS AND RELEVANCE

Severe rotavirus gastroenteritis was virtually absent among US children who had a genetic polymorphism that inactivates FUT2 expression on the intestinal epithelium. We observed a strong epidemiologic association among children with rotavirus gastroenteritis compared with healthy control participants. The exact cellular mechanism behind this epidemiologic association remains unclear, but evidence suggests that it may be rotavirus genotype specific. The lower prevalence of nonsecretors among Hispanic children may translate to an enhanced burden of rotavirus gastroenteritis among this group. Our findings may have bearing on our full understanding of rotavirus infections and the effects of vaccination in diverse populations.

Long-term Consistency in Rotavirus Vaccine Protection: RV5 and RV1 Vaccine Effectiveness in US Children, 2012-2013

BACKGROUND

Using a multicenter, active surveillance network from 2 rotavirus seasons (2012 and 2013), we assessed the vaccine effectiveness of RV5 (RotaTeq) and RV1 (Rotarix) rotavirus vaccines in preventing rotavirus gastroenteritis hospitalizations and emergency department (ED) visits for numerous demographic and secular strata.

METHODS

We enrolled children hospitalized or visiting the ED with acute gastroenteritis (AGE) for the 2012 and 2013 seasons at 7 medical institutions. Stool specimens were tested for rotavirus by enzyme immunoassay and genotyped, and rotavirus vaccination histories were compared for rotavirus-positive cases and rotavirus-negative AGE controls. We calculated the vaccine effectiveness (VE) for preventing rotavirus associated hospitalizations and ED visits for each vaccine, stratified by vaccine dose, season, clinical setting, age, predominant genotype, and ethnicity.

RESULTS

RV5-specific VE analyses included 2961 subjects, 402 rotavirus cases (14%) and 2559 rotavirus-negative AGE controls. RV1-specific VE analyses included 904 subjects, 100 rotavirus cases (11%), and 804 rotavirus-negative AGE controls. Over the 2 rotavirus seasons, the VE for a complete 3-dose vaccination with RV5 was 80% (confidence interval [CI], 74%-84%), and VE for a complete 2-dose vaccination with RV1 was 80% (CI, 68%-88%).Statistically significant VE was observed for each year of life for which sufficient data allowed analysis (7 years for RV5 and 3 years for RV1). Both vaccines provided statistically significant genotype-specific protection against predominant circulating rotavirus strains.

CONCLUSIONS

In this large, geographically and demographically diverse sample of US children, we observed that RV5 and RV1 rotavirus vaccines each provided a lasting and broadly heterologous protection against rotavirus gastroenteritis.

Epidemiological and Economic Impact of Monovalent and Pentavalent Rotavirus Vaccines in Low and Middle Income Countries: A Cost-effectiveness Modeling Analysis

BACKGROUND

The competing choices of vaccination with either RV1 or RV5, the potential budget impact of vaccines on the EPI with different prices and new evidence make important an updated analysis for health decision makers in each country. The objective of this study is to assess cost-effectiveness of the monovalent and pentavalent rotavirus vaccines and impact on children deaths, inpatient and outpatient visits in 116 low and middle income countries that represent approximately 99% of rotavirus mortality.

METHODS

A decision tree model followed hypothetical cohorts of children from birth up to 5 years of age for each country in 2010. Inputs were gathered from international databases and previous research on incidence and effectiveness of monovalent and pentavalent vaccines. Costs were expressed in 2010 international dollars. Outcomes were reported in terms of cost per disability-adjusted life-year averted, comparing no vaccination with either monovalent or pentavalent mass introduction. Vaccine price was assumed fixed for all world low-income and middle-income countries.

RESULTS

Around 292,000 deaths, 3.34 million inpatient cases and 23.09 million outpatient cases would occur with no vaccination. In the base-case scenario, monovalent vaccination would prevent 54.7% of inpatient cases and 45.4% of deaths. Pentavalent vaccination would prevent 51.4% of inpatient cases and 41.1% of deaths. The vaccine was cost-effective in all world countries in the base-case scenario for both vaccines. Cost per disability-adjusted life-year averted in all selected countries was I$372 for monovalent, and I$453 for pentavalent vaccination.

CONCLUSION

Rotavirus vaccine is cost-effective in most analyzed countries. Despite cost-effectiveness analysis is a useful tool for decision making in middle-income countries, for low-income countries health decision makers should also assess the impact of introducing either vaccine on local resources and budget impact analysis of vaccination.

Evidence of herd immunity and sustained impact of rotavirus vaccination on the reduction of rotavirus-related medical encounters among infants from 2006 through 2011 in the United States

BACKGROUND

Rotavirus (RV) is the leading cause of severe acute gastroenteritis among young children. Since the US licensure of the pentavalent RV vaccine (RV5) and the monovalent RV vaccine (RV1), a decline of RV activity has been observed.

OBJECTIVE

To describe patterns of RV-related health care utilization among infants receiving RV vaccines (RVVs).

METHODS

A large national health insurance claims database was used to identify infants born from January 2002 through July 2011. From this cohort, infants were divided into three groups: (1) those who received a RVV, (2) those receiving a diphtheria, tetanus, and acellular pertussis (DTaP) vaccine before the introduction of RVV (February 2006), and (3) those receiving DTaP without a concurrent RVV during the period of RVV availability. Study outcomes were rotavirus gastroenteritis (RGE) and acute gastroenteritis. Longitudinal, seasonal RGE incidence patterns among the RVV cohort (n = 140,952) were compared with the referent DTaP-vaccine cohort (n = 131,529).

RESULTS

More than 91% of administered RVV were RV5. Mean peak incidence of RV medical encounters in RV-vaccinated infants was 95-96% lower than among DTaP-vaccinated infants who did not receive RVV. RGE incidence among the non-RV-vaccinated DTaP recipients in the RVV-available period (110 per 100,000 infants) was lower than among DTaP recipients in the pre-RVV period (151 per 100,000 infants). The highest RGE incidence in the 2007-2011 period was among older non-RV-vaccinated infants.

CONCLUSIONS

Analysis of a national medical claims database indicates a sustained and substantial decrease in the seasonal RV medical claims pattern after the introduction of RVV. This analysis also reveals evidence of herd immunity, although unvaccinated infants continue to be at risk and contribute to smaller seasonal peaks in RV disease activity.

Insights from global data for use of rotavirus vaccines in India

Rotavirus vaccines are being introduced in several low- and middle-income countries across the world with and without support from the GAVI Alliance. India has the highest disease burden of rotavirus based on morbidity and mortality estimates and several indigenous vaccine manufacturers are developing rotavirus vaccines. One candidate has undergone phase III testing and others have completed evaluation in phase II. Global data on licensed vaccine performance in terms of impact on disease, strain diversity, safety and cost-effectiveness has been reviewed to provide a framework for decision making in India.

Pediatric small intestine bacterial overgrowth in low-income countries

Small intestine bacterial overgrowth (SIBO) occurs when colonic quantities of commensal bacteria are present in the small bowel. SIBO is associated with conditions of disrupted gastrointestinal (GI) motility leading to stasis of luminal contents. Recent data show that SIBO is also found in children living in unsanitary conditions who do not have access to clean water. SIBO leads to impaired micronutrient absorption and increased GI permeability, both of which may contribute to growth stunting in children. SIBO also disrupts mucosal immunity and has been implicated in oral vaccination underperformance and the development of celiac disease. SIBO in the setting of the impoverished human habitats may be an under-recognized cause of pediatric morbidity and mortality in the developing world.