Effectiveness of monovalent rotavirus vaccine in Bolivia: case-control study

Etiologies of Mild and Moderate Diarrheal Illness among Children in Consuelo, Dominican Republic

Since the rotavirus vaccine was included in the Dominican Republic's national immunization schedule in 2012, the microbiologic etiologies of acute gastroenteritis have not been described. This study aimed to determine the contribution of rotavirus as an etiology of acute gastroenteritis over a 12-month period in children under 5 years of age in both an inpatient and an outpatient setting in Consuelo, Dominican Republic. All children who were seen at Niños Primeros en Salud clinic or admitted to Hospital Municipal Dr. Angel Ponce Pinedo for acute gastroenteritis during January 2021-April 2022 were enrolled in the study. Stools were evaluated for rotavirus, enteric parasites, and pathogenic bacteria. Pathogen detection was compared between outpatients and inpatients and on the basis of child's vaccination status. From 181 children enrolled, 170 stool samples were collected, 28 (16.5%) from inpatients and 142 (83.5%) from outpatients. Rotavirus was the most commonly detected pathogen and was proportionately more common among hospitalized children, with nine (32.1%) cases among hospitalized children and 16 (11.3%) among outpatient children. (Pearson χ2 = 8.1, P = 0.004). Among patients with a positive rotavirus result, vaccination rate was lower among moderate (hospitalized) (three of six; 50%) compared with mild (outpatient) diarrhea patients (12 of 15; 80%). Giardia lamblia (10%) was the next most prevalent pathogen detected in both inpatients and outpatients using standard laboratory measures. Despite the availability of rotavirus vaccination, rotavirus remains a common cause of gastrointestinal illness among children under 5 years of age in our cohort. Incomplete vaccination status was associated with hospitalization for gastrointestinal illness.

Impact of rotavirus vaccination on diarrheal disease burden of children in South America

INTRODUCTION

Rotavirus is a leading cause of severe diarrheal disease and death in children under five years of age worldwide. Vaccination is one of the most important public health interventions to reduce this significant burden.

AREAS COVERED

This literature review examined vaccination coverage, hospitalization rate, mortality, genotypic distribution, immunogenicity, cost-effectiveness, and risk versus benefit of rotavirus vaccination in children in South America. Nine out of twelve countries in South America currently include a rotavirus vaccine in their national immunization program with coverage rates in 2022 above 90%.

EXPERT OPINION

Introduction of the rotavirus vaccination has led to a marked reduction in hospitalizations and deaths from diarrheal diseases in children under 5 years, particularly infants under 1 year, in several South American countries. In Brazil, hospitalizations decreased by 59% and deaths by 21% (30-38% in infants). In Peru, hospitalizations in infants fell by 46% and deaths by 37% (56% in infants). Overall, data suggest that rotavirus vaccination has reduced rotavirus deaths by 15-50% in various South American countries. There is some evidence that immunity wanes after the age of 1-year old. Ongoing surveillance of vaccine coverage and changes in morbidity and mortality is important to maximize protection against this disease.

Rotavirus Infection in Children <5 Years of Age in Suzhou, China, 2013-2019: Disease Burden, Genotype Distribution and Seasonality

BACKGROUND

This study aimed to determine the disease burden and strain distribution of rotavirus in children with diarrhea <5 years old in Suzhou, China.

METHODS

The study was conducted among children with diarrhea <5 years old at Suzhou University Affiliated Children's Hospital from 2013 to 2019. Rotavirus antigen was detected in clinical laboratory and then sent to Suzhou Centers for Disease Control and Prevention for further molecular analysis. Group A rotavirus (RVA) was detected through enzyme-linked immunosorbent assays, and G-genotype and P-genotype of RVA were tested using reverse transcription-polymerase chain reaction.

RESULTS

Of a total of 198,130 children with diarrhea, 70,813 (35.7%) were positive for RVA; RVA-related diarrhea was detected in 7798 (20.7%, n = 7798/37,710) inpatients and 63,015 (39.3%, n = 63,015/160,420) outpatients. Most children (92.0%, n = 65,171/70,813) positive for RVA were found as children <3 years old. Children 12-35 months old were reported as the highest prevalence among all age groups. The seasonal peak of RVA was in the autumn and winter. Among all 673 RVA strains genotyped, the G9P[8] strain was reported to be persistently predominant in the pediatric population from 2013 to 2019.

CONCLUSIONS

The burden of diarrhea disease due to rotavirus infection remains high in Suzhou.

Community-level interventions for mitigating the risk of waterborne diarrheal diseases: a systematic review

BACKGROUND

Waterborne diarrhea diseases are among the leading causes of morbidity and mortality globally. These diseases can be mitigated by implementing various interventions. We reviewed the literature to identify available interventions to mitigate the risk of waterborne diarrheal diseases.

METHODS

We conducted a systematic database review of CINAHL (Cumulative Index to Nursing and Allied Health Literature), PubMed, Web of Science Core Collection, Cochrane library, Scopus, African Index Medicus (AIM), and LILACS (Latin American and Caribbean Health Sciences Literature). Our search was limited to articles published between 2009 and 2020. We conducted the review using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement checklist. The identified studies were qualitatively synthesized.

RESULTS

Our initial search returned 28 773 articles of which 56 studies met the inclusion criteria. The included studies reported interventions, including vaccines for rotavirus disease (monovalent, pentavalent, and Lanzhou lamb vaccine); enhanced water filtration for preventing cryptosporidiosis, Vi polysaccharide for typhoid; cholera 2-dose vaccines, water supply, water treatment and safe storage, household disinfection, and hygiene promotion for controlling cholera outbreaks.

CONCLUSION

We retrieved few studies on interventions against waterborne diarrheal diseases in low-income countries. Interventions must be specific to each type of waterborne diarrheal disease to be effective. Stakeholders must ensure collaboration in providing and implementing multiple interventions for the best outcomes.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42020190411 .

Understanding Rotavirus Vaccine Efficacy and Effectiveness in Countries with High Child Mortality

Rotavirus claims thousands of lives of children globally every year with a disproportionately high burden in low- and lower-middle income countries where access to health care is limited. Oral, live-attenuated rotavirus vaccines have been evaluated in multiple settings in both low- and high-income populations and have been shown to be safe and efficacious. However, the vaccine efficacy observed in low-income settings with high rotavirus and diarrheal mortality was significantly lower than that seen in high-income populations where rotavirus mortality is less common. Rotavirus vaccines have been introduced and rolled out in more than 112 countries, providing the opportunity to assess effectiveness of the vaccines in these different settings. We provide an overview of the efficacy, effectiveness, and impact of rotavirus vaccines, focusing on high-mortality settings and identify the knowledge gaps for future research. Despite lower efficacy, rotavirus vaccines substantially reduce diarrheal disease and mortality and are cost-effective in countries with high burden. Continued evaluation of the effectiveness, impact, and cost-benefit of rotavirus vaccines, especially the new candidates that have been recently approved for global use, is a key factor for new vaccine introductions in countries, or for a switch of vaccine product in countries with limited resources.

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.

Global Experience with Rotavirus Vaccines

Rotavirus is a major cause of severe pediatric diarrhea worldwide. In 2006, two live, oral rotavirus vaccines, Rotarix and RotaTeq, were licensed for use in infants and were rapidly adopted in many high- and middle-income settings where efficacy had been demonstrated in clinical trials. Following completion of additional successful trials in low-income settings, the World Health Organization (WHO) recommended rotavirus vaccination for all infants globally in 2009. In 2018, two new rotavirus vaccines, Rotasiil and Rotavac, were prequalified by WHO, further expanding global availability. As of March 2021, rotavirus vaccines have been introduced nationally in 106 countries. Since introduction, rotavirus vaccines have demonstrated effectiveness against severe disease and mortality, even among age groups not eligible for vaccination. Cross-genotypic protection has also been demonstrated, and the favorable benefit-risk profile of these vaccines continues to be confirmed via post-marketing surveillance. Ongoing research seeks to better understand reasons for the lower effectiveness observed in lower-resource settings, and to use these findings to optimize vaccine strategies worldwide.

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 performance of licensed rotavirus vaccines and the development of a new generation of rotavirus vaccines: a review

Rotavirus, which causes acute gastroenteritis and severe diarrhea, has posed a great threat to children worldwide over the last 30 y. Since no specific drugs and therapies against rotavirus are available, vaccination is considered the most effective method of decreasing the morbidity and mortality related to rotavirus-associated gastroenteritis. To date, six rotavirus vaccines have been developed and licensed by local governments. Notably, Rotarix™ and RotaTeq™ have been recommended as universal agents against rotavirus infection by the World Health Organization; however, lower efficacies were found in less-developed and developing regions with medium and high child mortality than well-developed ones with low child mortality. For now, two promising novel vaccines, Rotavac™ and RotaSiil™ were pre-qualified by the World Health Organization in 2018. Other rotavirus vaccines in the pipeline including neonatal strain (RV3-BB) and several non-replicating rotavirus vaccines with a parenteral delivery strategy are currently undergoing investigation, with the potential to improve the performance of, and eliminate the safety concerns associated with, previous live oral rotavirus vaccines. This paper reviews the important developments in rotavirus vaccines in the last 20 y and discusses problems and challenges that require investigation in the future.

Real-world effectiveness of rotavirus vaccines, 2006-19: a literature review and meta-analysis

BACKGROUND

Since licensure in 2006, rotavirus vaccines have been introduced in more than 100 countries. The efficacy of rotavirus vaccines is variable in settings with different child mortality levels. We did an updated review of the published literature to assess the real-world effectiveness of rotavirus vaccines in a range of settings.

METHODS

In this literature review and meta-analysis, we included observational, post-licensure studies of rotavirus vaccines, published from Jan 1, 2006, to Dec 31, 2019, in English, with laboratory-confirmed rotavirus as the endpoint. In addition to product-specific results for Rotarix (GlaxoSmithKline Biologicals, Rixensart, Belgium) or RotaTeq (Merck, West Point, PA, USA), we included Rotarix and RotaTeq mixed series, and non-product-specific vaccine effectiveness estimates from countries where Rotarix and RotaTeq are both available. Studies of other infant rotavirus vaccines were excluded because little or no post-licensure data were available. We fitted random-effects regression models to estimate vaccine effectiveness among children younger than 12 months and aged 12-23 months. On the basis of 2017 UNICEF mortality estimates for children younger than 5 years, countries were stratified as having low (lowest quartile), medium (second quartile), or high mortality (third and fourth quartiles).

FINDINGS

We identified and screened 1703 articles, of which 60 studies from 32 countries were included. 31 studies were from countries with low child mortality, eight were from medium-mortality countries, and 21 were from high-mortality countries. Rotarix vaccine effectiveness against laboratory-confirmed rotavirus among children younger than 12 months old was 86% (95% CI 81-90) in low-mortality countries, 77% (66-85) in medium-mortality countries, and 63% (54-70) in high-mortality countries. Rotarix vaccine effectiveness among children aged 12-23 months was 86% (81-90) in low-mortality countries, 54% (23-73) in medium-mortality countries, and 58% (38-72) in high-mortality countries. RotaTeq vaccine effectiveness among children younger than 12 months was 86% (76-92) in low-mortality countries and 66% (51-76) in high-mortality countries. RotaTeq vaccine effectiveness among children aged 12-23 months was 84% (79-89) in low-mortality countries. There was no substantial heterogeneity (I² range: 0-36%). Median vaccine effectiveness in low-mortality countries was similar for Rotarix (83%; IQR 78-91), RotaTeq (85%; 81-92), mixed series (86%; 70-91), and non-product-specific (89%; 75-91) vaccination.

INTERPRETATION

Rotavirus vaccines were effective in preventing rotavirus diarrhoea, with higher performance in countries with lower child mortality.

FUNDING

None.

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.

The Use of Test-negative Controls to Monitor Vaccine Effectiveness: A Systematic Review of Methodology

BACKGROUND

The test-negative design is an increasingly popular approach for estimating vaccine effectiveness (VE) due to its efficiency. This review aims to examine published test-negative design studies of VE and to explore similarities and differences in methodological choices for different diseases and vaccines.

METHODS

We conducted a systematic search on PubMed, Web of Science, and Medline, for studies reporting the effectiveness of any vaccines using a test-negative design. We screened titles and abstracts and reviewed full texts to identify relevant articles. We created a standardized form for each included article to extract information on the pathogen of interest, vaccine(s) being evaluated, study setting, clinical case definition, choices of cases and controls, and statistical approaches used to estimate VE.

RESULTS

We identified a total of 348 articles, including studies on VE against influenza virus (n = 253), rotavirus (n = 48), pneumococcus (n = 24), and nine other pathogens. Clinical case definitions used to enroll patients were similar by pathogens of interest but the sets of symptoms that defined them varied substantially. Controls could be those testing negative for the pathogen of interest, those testing positive for nonvaccine type of the pathogen of interest, or a subset of those testing positive for alternative pathogens. Most studies controlled for age, calendar time, and comorbidities.

CONCLUSIONS

Our review highlights similarities and differences in the application of the test-negative design that deserve further examination. If vaccination reduces disease severity in breakthrough infections, particular care must be taken in interpreting vaccine effectiveness estimates from test-negative design studies.

Genotype distribution of Group A rotavirus in children before and after massive vaccination in Latin America and the Caribbean: Systematic review

BACKGROUND

During the last decade, most of Latin American and the Caribbean (LAC) countries have implemented oral live rotavirus vaccines in their national vaccination programs with remarkable results. However, it has been suggested that massive vaccination could lead to the replacement of circulating genotypes or the emergence of new variants or neutralizing antibodies escape mutants, which may reduce the effectiveness of the vaccine. The objective was to analyze the genetic diversity of Group A rotavirus before and after the introduction of universal vaccination in LAC.

METHODS

We conducted a systematic review of studies published in PubMed, Scielo and LILACS. There were considered only LAC countries with rotavirus massive vaccination strategy which had described circulating genotypes data in children under 5 years of age, either for surveillance or vaccine effectiveness purposes, from 2001 to 2017. Systematic review stages were carried out following the recommendations of PRISMA.

RESULTS

Of the 18 countries that included any of the two licensed rotavirus vaccines in their national schedules since 2006, only 7 (~39%) presented studies of RVA genetic diversity before and after implementation, and met the inclusion criteria. Four of them (Argentina, Brazil, Colombia and Nicaragua) experienced a rapid switch from Wa-like to DS-1-like strains. Also, G1P[8] association, considered the most predominant worldwide in the pre-vaccination era, decreased significantly and was only frequently detected in Venezuela and Nicaragua. No defined pattern of emergence at high frequencies of unusual associations was observed in the post vaccination period, except for some evidence of G9P[4] in Colombia, G3P[6] and G1P[4] in Nicaragua.

CONCLUSIONS

Even though the evidence shows a DS-1-like change trend, data from studies conducted in Latin America and the Caribbean are diverse and still not sufficient to assess the impact of vaccines on viral ecology or if genetic diversity is influenced by natural mechanisms of fluctuation.

Introducing new vaccines in low- and middle-income countries: challenges and approaches

INTRODUCTION

The number of new vaccine introductions (NVIs) in low and middle-income countries (LMICs) has markedly increased since 2010, raising challenges to often overstretched and underfunded health care systems.

AREAS COVERED

We present an overview of some of these challenges, focusing on programmatic decisions, delivery strategy, information and communication, pharmacovigilance and post-licensure evaluation. We also highlight field-based initiatives that may facilitate NVI.

EXPERT COMMENTARY

Some new vaccines targeting populations other than infants require alternative delivery strategies. NVIs impact upon existing supply chain management, in particular vaccines with novel characteristics. A lack of understanding about immunization and misconceptions may be detrimental to NVI, as well as insufficient or poorly trained health care workforce. Many barriers exist to achieving good vaccination coverage. Real-world evaluation of vaccine safety, effectiveness and impact in LMICs may be limited by lack of robust demographic and disease epidemiology data, as well as limited health care and surveillance infrastructure. A thorough planning phase is crucial to define the most suitable delivery strategy based on the vaccine's and country's specificities. A communication plan and social mobilization are essential. Implementation research and innovative approaches applied to logistics, delivery, communication and program evaluation can facilitate NVI.

Prevalence of rotavirus and rapid changes in circulating rotavirus strains among children with acute diarrhea in China, 2009-2015

BACKGROUND

Rotavirus is a leading cause of morbidity and mortality in young children worldwide. In China, the universal immunization of children with the rotavirus vaccine has not been introduced, and the two globally distributed vaccines (RotaTeq and Rotarix) are not licensed in the country. We aim to determine the prevalence and strain diversity of rotavirus in children with diarrhea aged ≤ five years across China.

MATERIALS AND METHODS

Sentinel-based surveillance of acute diarrhea was conducted at 213 participating hospitals in China from January 1, 2009, through December 31, 2015. Group A rotavirus (RVA) was tested by using enzyme-linked immunosorbent assays, and G- and P-genotype of RVA were tested by RT-PCR methods.

RESULTS

Of 33,616 children with diarrhea, 10,089 (30%) were positive for RVA; RVA-associated diarrhea was identified in 2247 (39.5%, n = 2247/5685) inpatients and 7842 (28.1%, n = 7842/27931) outpatients. Children living in low-middle-income regions suffered from the highest burden of rotavirus, with 40.7% of diarrhea cases attributed to rotavirus infection, followed by 31.3% in upper-middle-income and 11.2% in high-income regions. The majority of children (88.9%, n = 8976/10089) who tested positive for RVA were children aged ≤ 2 years. The seasonal peak of RVA was in the winter. Among all 2533 RVA strains genotyped, five strain combinations, G9P[8], G3P[8], G1P[8], G2P[4] and G3P[4], contributed to 71.3% (1807/2533) of the RVA-associated diarrhea cases. The predominant strain of RVA has rapidly evolved from G3P[8] and G1P[8] to G9P[8] in the recent years, with the proportion of G9P[8] having increased remarkably from 3.4% in 2009 to 60.9% in 2015.

CONCLUSIONS

The burden of diarrhea attributed to rotavirus is high in China, highlighting the potential value of vaccination. The rapid shift of RVA strains highlights the importance of conducting rotavirus surveillance to ensure that currently marketed vaccines provide protective efficacy against the circulating strains.

Effectiveness of the Oral Human Attenuated Rotavirus Vaccine: A Systematic Review and Meta-analysis-2006-2016

Background

Gastroenteritis caused by rotavirus accounts for considerable morbidity in young children. We aimed to assess the vaccine effectiveness (VE) of the oral rotavirus vaccine Rotarix, as measured by laboratory-confirmed rotavirus infection after referral to hospital and/or emergency departments in children aged <5 years with gastroenteritis.

Methods

We performed a systematic search for peer-reviewed studies conducted in real-life settings published between 2006 and 2016 and a meta-analysis to calculate the overall Rotarix VE, which was further discriminated through stratified analyses.

Results

The overall VE estimate was 69% (95% confidence interval [CI], 62% to 75%); stratified analyses revealed a non-negligible impact of factors such as study design and socioeconomic status. Depending on the control group, VE ranged from 63% (95% CI, 52% to 72%) to 81% (95% CI, 69% to 88%) for unmatched and matched rotavirus test–negative controls. VE varied with socioeconomic status: 81% (95% CI, 74% to 86%) in high-income countries, 54% (95% CI, 39% to 65%) in upper-middle-income countries, and 63% (95% CI, 50% to 72%) in lower-middle-income countries. Age, rotavirus strain, and disease severity were also shown to impact VE, but to a lesser extent.

Conclusions

This meta-analysis of real-world studies showed that Rotarix is effective in helping to prevent hospitalizations and/or emergency department visits due to rotavirus infection.

Effect of Age at Vaccination on Rotavirus Vaccine Effectiveness in Bolivian Infants

BACKGROUND

Rotavirus vaccines are less effective in developing countries versus developed countries. One hypothesis for this difference in performance is that higher levels of maternal antibodies in developing countries may interfere with vaccine response, suggesting that delayed dosing could be beneficial. The present analysis aims to assess whether rotavirus vaccine effectiveness (VE) varies by age at vaccination during routine use in Bolivia.

METHODS

Data were merged from 2 postlicensure evaluations of monovalent rotavirus vaccine (RV1) in Bolivia, where 2 doses of RV1 are recommended at 2 and 4 months of age. For each dose, children were classified as receiving each dose "early," "on-time" or "late." Stratified unconditional logistic regression models were used to estimate VE, using unvaccinated children as the referent. VE was calculated as (1 - odds ratio) × 100%. Models were adjusted for hospital, age and time since RV1 introduction (via including terms for month and year of birth).

RESULTS

VE for 2 doses of RV1 tended to be higher in infants receiving the first dose early (VE, 92%; 95% confidence interval: 70%-98%), when compared with infants receiving their first dose on-time [72% (62%-81%)] or late [68% (51%-79%)]. Estimates of VE were not substantially different when comparing children by age at second dose [early: VE, 76% (50%-89%); on-time: VE, 70% (50%-89%); late: VE, 75% (60%, 84%)], including all children.

CONCLUSIONS

Our results indicate that early administration may improve VE and support the current World Health Organization recommendations for the RV1 schedule.

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.

Impact of routine rotavirus vaccination on all-cause and rotavirus hospitalizations during the first four years following vaccine introduction in Rwanda

BACKGROUND

Rwanda introduced pentavalent rotavirus vaccine into its national immunization program in 2012. To determine the long-term impact of rotavirus vaccine on disease burden in a high burden setting, we examined trends in rotavirus and all-cause diarrhea hospitalizations in the first four years following rotavirus vaccine introduction.

METHODS

We used data from an active surveillance system, from a review of pediatric ward registries, and from the Health Management Information System to describe trends in rotavirus and all-cause diarrhea hospitalizations from January 2009 through December 2016. Percent reductions were calculated to compare the number of all-cause and rotavirus diarrhea hospitalizations pre- and post-rotavirus vaccine introduction.

RESULTS

The proportion of diarrhea hospitalizations due to rotavirus declined by 25-44% among all children <5 years of age during 2013-2015 with a shift in rotavirus hospitalizations to older age groups. The proportion of total hospitalizations due to diarrhea among children <5 years of age decreased from 19% pre-vaccine introduction to 12-13% post-vaccine introduction. In the national hospital discharge data, substantial decreases were observed in all-cause diarrhea hospitalizations among children <5 years of age in 2013 and 2014 but these gains lessened in 2015-2016.

DISCUSSION

Continued monitoring of long-term trends in all-cause diarrhea and rotavirus hospitalizations is important to ensure that the impact of the vaccination program is sustained over time and to better understand the changing age dynamics of diarrhea and rotavirus hospitalizations in the post-vaccine introduction era.

Distribution of rotavirus genotypes associated with acute diarrhoea in Zimbabwean children less than five years old before and after rotavirus vaccine introduction

BACKGROUND

Sentinel surveillance for diarrhoea is important to monitor changes in rotavirus epidemiological trends and circulating genotypes among children under 5 years before and after vaccine introduction. The Zimbabwe Ministry of Health and Child Care introduced rotavirus vaccine in national immunization program in May 2014.

METHODS

Active hospital-based surveillance for diarrhoea was conducted at 3 sentinel sites from 2008 to 2016. Children aged less than 5 years, who presented with acute gastroenteritis as a primary illness and who were admitted to a hospital ward or treated at the emergency unit, were enrolled and had a stool specimen collected and tested for rotavirus by enzyme immunoassay (EIA). Genotyping of positive stools was performed using reverse-transcription polymerase chain reaction and genotyping assays. Pre-vaccine introduction, 10% of all positive stool specimens were genotyped and all adequate positive stools were genotyped post-vaccine introduction.

RESULTS

During the pre-vaccine period, a total of 6491 acute gastroenteritis stools were collected, of which 3016 (46%) tested positive for rotavirus and 312 (10%) of the rotavirus positive stools were genotyped. During the post-vaccine period, a total of 3750 acute gastroenteritis stools were collected, of which 937 (25%) tested positive for rotavirus and 784 (84%) were genotyped. During the pre-vaccine introduction the most frequent genotype was G9P[8] (21%) followed by G2P[4] (12%), G1P[8] (6%), G2P[6] (5%), G12P[6] (4%), G9P[6] (3%) and G8P[4] (3%). G1P[8] (30%) was most dominant two years after vaccine introduction followed by G9P[6] (20%), G2P[4] (15%), G9P[8] (11%) and G1P[6] (4%).

CONCLUSION

The decline in positivity rate is an indication of early vaccine impact. Diversity of circulating strains underscores the importance of continued monitoring and strain surveillance after vaccine introduction.

Observational studies and the difficult quest for causality: lessons from vaccine effectiveness and impact studies

Although randomized placebo-controlled trials (RCT) are critical to establish efficacy of vaccines at the time of licensure, important remaining questions about vaccine effectiveness (VE)-used here to include individual-level measures and population-wide impact of vaccine programmes-can only be answered once the vaccine is in use, from observational studies. However, such studies are inherently at risk for bias. Using a causal framework and illustrating with examples, we review newer approaches to detecting and avoiding confounding and selection bias in three major classes of observational study design: cohort, case-control and ecological studies. Studies of influenza VE, especially in seniors, are an excellent demonstration of the challenges of detecting and reducing such bias, and so we use influenza VE as a running example. We take a fresh look at the time-trend studies often dismissed as 'ecological'. Such designs are the only observational study design that can measure the overall effect of a vaccination programme [indirect (herd) as well as direct effects], and are in fact already an important part of the evidence base for several vaccines currently in use. Despite the great strides towards more robust observational study designs, challenges lie ahead for evaluating best practices for achieving robust unbiased results from observational studies. This is critical for evaluation of national and global vaccine programme effectiveness.

Decreased performance of live attenuated, oral rotavirus vaccines in low-income settings: causes and contributing factors

INTRODUCTION

Numerous studies have shown that the oral rotavirus vaccines are less effective in infants born in low income countries compared to those born in developed countries. Identifying the specific factors in developing countries that decrease and/or compromise the protection that rotavirus vaccines offer, could lead to a path for designing new strategies for the vaccines' improvement.

AREAS COVERED

We accessed PubMed to identify rotavirus vaccine performance studies (i.e., efficacy, effectiveness and immunogenicity) and correlated performance with several risk factors. Here, we review the factors that might contribute to the low vaccine efficacy, including passive transfer of maternal rotavirus antibodies, rotavirus seasonality, oral polio vaccine (OPV) administered concurrently, microbiome composition and concomitant enteric pathogens, malnutrition, environmental enteropathy, HIV, and histo blood group antigens.

EXPERT COMMENTARY

We highlight two major factors that compromise rotavirus vaccines' efficacy: the passive transfer of rotavirus IgG antibodies to infants and the  co-administration of rotavirus vaccines with OPV. We also identify other potential risk factors that require further research because the data about their interference with the efficacy of rotavirus vaccines are inconclusive and at times conflicting.

Potential for a booster dose of rotavirus vaccine to further reduce diarrhea mortality

Concern has grown that children vaccinated against rotavirus in developing countries may be vulnerable to rotavirus diarrhea in the second year of life due to waning immunity. Adding a booster dose of rotavirus vaccine at 9 or 12 months of age with measles vaccine has been suggested as a strategy to address this. We evaluated the hypothetical potential benefits of a booster dose on reduction of rotavirus mortality. The projected number of deaths averted were calculated using national level full series vaccination coverage, estimated national rotavirus deaths by week of age, and VE at <12 months of age and ≥12 months of age derived from the published literature. We assumed three functional forms of waning based on the VE estimates: stepwise, linear, and logarithmic. We modeled three potential boosting scenarios: (a) reduced VE waning in the second year of life by 50%, (b) reestablished second year of life VE to the levels in the first year of life, and (c) boosted first year VE by 50% of the difference between VE in the first and second years. To express uncertainty resulting from the parameters, each of the nine models were run 1000 times using a random sample of input values. Across all WHO regions, with the stepwise models we estimated a median of 9800 (95%CI: 9400, 10,200), 19,600 (95%CI: 18,800, 20,400), and 29,400 (95%CI: 28,200, 30,700) additional rotavirus deaths averted in the reduced VE waning, reestablished VE, and boosted VE scenarios. These estimates were highly sensitive to the assumed functional form of waning with approximately 65-80% fewer deaths averted if immunity waned in a linear or logarithmic fashion compared to the stepwise model. While these projections will benefit from improved input data points, our resultsinform consideration of booster doses of rotavirus vaccine.

Population effectiveness of the pentavalent and monovalent rotavirus vaccines: a systematic review and meta-analysis of observational studies

BACKGROUND

Rotavirus was the leading cause of acute gastroenteritis (AGE) in infants and young children prior to the introduction of routine vaccination. Since 2006 there have been two licensed vaccines available; with successful clinical trials leading the World Health Organization to recommend rotavirus vaccination for all children worldwide. In order to inform immunisation policy we have conducted a systematic review and meta-analysis of observation studies to assess population effectiveness against acute gastroenteritis.

METHODS

We systematically searched PubMed, Medline, Web of Science, Cinhal and Academic Search Premier and grey literature sources for studies published between January 2006 and April 2014. Studies were eligible for inclusion if they were observational measuring population effectiveness of rotavirus vaccination against health care attendances for rotavirus gastroenteritis or AGE. To evaluate study quality we use used the Newcastle-Ottawa Scale for non-randomised studies, categorising studies by risk of bias. Publication bias was assessed using funnel plots. If two or more studies reported a measure of vaccine effectiveness (VE), we conducted a random effects meta-analysis. We stratified analyses by World Bank country income level and used study quality in sensitivity analyses.

RESULTS

We identified 30 studies, 19 were from high-income countries and 11 from middle-income countries. Vaccine effectiveness against hospitalization for laboratory confirmed rotavirus gastroenteritis was highest in high-income countries (89% VE; 95% CI 84-92%) compared to middle-income countries (74% VE; 95% CI 67-80%). Vaccine effectiveness was higher for those receiving the complete vaccine schedule (81% VE; 95% CI 75-86%) compared to partial schedule (62% VE; 95% CI 55-69%). Two studies from high-income countries measured VE against community consultations for AGE with a pooled estimate of 40% (95% CI 13-58%; 2 studies).

CONCLUSIONS

We found strong evidence to further support the continued use of rotavirus vaccines. Vaccine effectiveness was similar to that reported in clinical trials for both high and middle-income countries. There is limited data from Low income settings at present. There was lower effectiveness against milder disease. Further studies, should continue to report effectiveness against AGE and less-severe rotavirus disease because as evidenced by pre-vaccine introduction studies this is likely to contribute the greatest burden on healthcare resources, particularly in high-income countries.

Efficacy, safety and effectiveness of licensed rotavirus vaccines: a systematic review and meta-analysis for Latin America and the Caribbean

BACKGROUND

RotaTeq™ (RV5; Merck & Co. Inc., USA) and Rotarix™ (RV1, GlaxoSmithKline, Belgium) vaccines, developed to prevent rotavirus diarrhea in children under five years old, were both introduced into national immunization programs in 2006. As many countries in Latin America and the Caribbean have included either RV5 or RV1 in their routine childhood vaccination programs, we conducted a systematic review and meta-analysis to analyze efficacy, safety and effectiveness data from the region.

METHODS

We conducted a systematic search in PubMed, EMBASE, Scielo, Lilacs and the Cochrane Central Register, for controlled efficacy, safety and effectiveness studies published between January 2000 until December 2011, on RV5 and RV1 across Latin America (where both vaccines are available since 2006). The primary outcome measures were: rotavirus-related gastroenteritis of any severity; rotavirus emergency department visits and hospitalization; and severe adverse events.

RESULTS

The results of the meta-analysis for efficacy show that RV1 reduced the risk of any-severity rotavirus-related gastroenteritis by 65% (relative risk (RR) 0.35, 95% confidence interval (CI) 0.25; 0.50), and of severe gastroenteritis by 82% (RR 0.18, 95%CI 0.12; 0.26) versus placebo. In trials, both vaccines significantly reduced the risk of hospitalization and emergency visits by 85% (RR 0.15, 95%CI 0.09; 0.25) for RV1 and by 90% (RR 0.099, 95%CI 0.012; 0.77) for RV5. Vaccination with RV5 or RV1 did not increase the risk of death, intussusception, or other severe adverse events which were previously associated with the first licensed rotavirus vaccine. Real-world effectiveness studies showed that both vaccines reduced rotavirus hospitalization in the region by around 45-50% for RV5 (for 1 to 3 doses, respectively), and, by around 50-80% for RV1 (for 1 to 2 doses, respectively). For RV1, effectiveness against hospitalization was highest (around 80-96%) for children vaccinated before 12 months of age, compared with 5-60% effectiveness in older children. Both vaccines were most effective in preventing more severe gastroenteritis (70% for RV5 and 80-90% for RV1) and severe gastroenteritis (50% for RV5 and 70-80% for RV1).

CONCLUSION

This systematic literature review confirms rotavirus vaccination has been proven effective and well tolerated in protecting children in Latin America and the Caribbean.

Impact of Rotavirus Vaccine Introduction and Vaccine Effectiveness in the Republic of Moldova

BACKGROUND

The Republic of Moldova was the first low- to middle-income country in the World Health Organization European Region to introduce rotavirus vaccine (July 2012). We aimed to assess the impact of the rotavirus vaccine program and estimate vaccine effectiveness (VE).

METHODS

Surveillance for rotavirus gastroenteritis was conducted in 2 hospitals in the capital city of Chisinau starting in September 2009. Monthly rotavirus admissions by age were examined before and after introduction of rotavirus vaccination using interrupted time-series analyses. We performed a case-control study of VE by comparing rotavirus case patients with test-negative controls.

RESULTS

Coverage with at least 1 dose of vaccine increased from 35% in year 1 to 55% in year 2 for children <1 year of age. The percentage of hospital admissions positive for rotavirus fell from 45% in the prevaccine period to 25% (rate reduction, 36%; 95% confidence interval [CI], 26%-44%) and 14% (rate reduction, 67%; 95% CI, 48%-88%) in the first and second years after vaccine introduction, respectively, among children aged <5 years. Reductions were most pronounced among those aged <1 year. Significant reductions among cohorts too old to be vaccinated suggest indirect benefits. Two-dose VE was 79% (95% CI, 62%-88%) against rotavirus hospitalization and 84% (95% CI, 64%-93%) against moderate to severe rotavirus.

CONCLUSIONS

These results consistently point to profound direct and herd immunity impacts of the rotavirus vaccine program in young children in the Republic of Moldova. Vaccine coverage was modest in these early years following introduction, so there remains potential for further disease reductions.

Sustained Effectiveness of Rotavirus Vaccine Against Very Severe Rotavirus Disease Through the Second Year of Life, Bolivia 2013-2014

BACKGROUND

In Bolivia, monovalent rotavirus vaccine was introduced in 2008 and a previous evaluation reported a vaccine effectiveness (VE) of 77% with 2 doses of vaccine in children aged <3 years. This evaluation sought to determine if rotavirus vaccine provided protection through the second year of life against circulating genotypes.

METHODS

A case-control study was performed in 5 hospitals from April 2013 to March 2014. Among enrolled participants who met study criteria and had rotavirus stool testing performed and vaccine status confirmed, we calculated VE using a logistic regression model. Subgroup analyses were performed among children aged <1 year and those aged ≥1 year, among children with severe diarrhea (Vesikari score ≥11) and very severe diarrhea (Vesikari score ≥15), and among G and P strains with at least 40 specimens.

RESULTS

A total of 776 children were enrolled. For children <1 year and ≥1 year of age with severe diarrhea, VE for 2 doses was 75% (95% confidence interval [CI], 46%-88%) and 53% (95% CI, 9%-76%), respectively. For children <1 year and ≥1 year of age with very severe diarrhea, VE for 2 doses was 80% (95% CI, 44%-93%) and 74% (95% CI, 35%-90%), respectively. Genotype-specific analysis demonstrated similar VE for the 4 most common G and P types (G3, G9, P[6] and P[8]).

CONCLUSIONS

A monovalent rotavirus vaccine remains effective against a broad range of circulating strains as part of a routine immunization program >5 years after its introduction in Bolivia. Although VE appears to wane in children aged ≥1 year, it still provides significant protection, and does not wane against severe disease.

Effectiveness of Monovalent Rotavirus Vaccine After Programmatic Implementation in Botswana: A Multisite Prospective Case-Control Study

BACKGROUND

Botswana introduced monovalent G1P rotavirus vaccine (RV1) in July 2012, providing one of the first opportunities to assess the effectiveness of routine RV1 vaccination in a high-burden setting in Africa. We sought to determine the effectiveness of RV1 against rotavirus diarrhea hospitalization using a case-control evaluation.

METHODS

Vaccine age-eligible children <5 years of age admitted with diarrhea at 4 hospitals in Botswana were enrolled from June 2013 to April 2015. Card-confirmed vaccine history was compared between case patients (children with laboratory-confirmed rotavirus diarrhea) and nonrotavirus "test-negative" diarrhea controls. Vaccine effectiveness (VE) was computed using unconditional logistic regression models adjusting for age, birth month/year, and hospital. Sequence-based genotyping was performed on antigen-positive samples.

RESULTS

Among 242 case patients and 368 controls, 82% (199/242) and 92% (339/368), respectively, had received ≥1 doses of RV1. Effectiveness of a full series (2 doses) of RV1 against rotavirus diarrhea requiring hospitalization was 54% (95% confidence interval [CI], 23%-73%); 1 dose of RV1 was 48% (95% CI, 1%-72%) effective. Effectiveness was 59% (95% CI, 4%-83%) against rotavirus caused by G2P, the most common (37%) circulating genotype. However, the effectiveness of 2 RV1 doses was significantly higher in children with no undernutrition (VE, 75% [95% CI, 41%-89%]), compared to those with moderate or severe undernutrition (VE, -28% [95% CI, -309% to 60%]) (P= .02).

CONCLUSIONS

Routine RV1 vaccination in Botswana showed effectiveness similar to that in clinical trials in Africa, including against a serotype fully heterotypic to the vaccine. Undernutrition may in part explain the lower rotavirus VE in low-income settings.

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.

Rotavirus vaccine effectiveness in low-income settings: An evaluation of the test-negative design

BACKGROUND

The test-negative design (TND), an epidemiologic method currently used to measure rotavirus vaccine (RV) effectiveness, compares the vaccination status of rotavirus-positive cases and rotavirus-negative controls meeting a pre-defined case definition for acute gastroenteritis. Despite the use of this study design in low-income settings, the TND has not been evaluated to measure rotavirus vaccine effectiveness.

METHODS

This study builds upon prior methods to evaluate the use of the TND for influenza vaccine using a randomized controlled clinical trial database. Test-negative vaccine effectiveness (VE-TND) estimates were derived from three large randomized placebo-controlled trials (RCTs) of monovalent (RV1) and pentavalent (RV5) rotavirus vaccines in sub-Saharan Africa and Asia. Derived VE-TND estimates were compared to the original RCT vaccine efficacy estimates (VE-RCTs). The core assumption of the TND (i.e., rotavirus vaccine has no effect on rotavirus-negative diarrhea) was also assessed.

RESULTS

TND vaccine effectiveness estimates were nearly equivalent to original RCT vaccine efficacy estimates. Neither RV had a substantial effect on rotavirus-negative diarrhea.

CONCLUSIONS

This study supports the TND as an appropriate epidemiologic study design to measure rotavirus vaccine effectiveness in low-income settings.

A Systematic Review of the Effect of Rotavirus Vaccination on Diarrhea Outcomes Among Children Younger Than 5 Years

BACKGROUND

Rotavirus is the leading cause of vaccine-preventable diarrhea among children under 5 globally. Rotavirus vaccination has been shown to prevent severe rotavirus infections with varying efficacy and effectiveness by region.

METHODS

We sought to generate updated region-specific estimates of rotavirus vaccine efficacy and effectiveness. We systematically reviewed published vaccine efficacy and effectiveness studies to assess the region-specific effect of rotavirus vaccination on select diarrheal morbidity and mortality outcomes in children under 5 years of age. We employed meta-analytic methods to generate pooled effect sizes by Millennium Development Goal region.

RESULTS

Rotavirus vaccination was both efficacious and effective in preventing rotavirus diarrhea, severe rotavirus diarrhea and rotavirus hospitalizations among children under 5 across all regions represented by the 48 included studies. Efficacy against severe rotavirus diarrhea ranged from 90.6% [95% confidence interval (CI): 82.3-95.0] in the developed region to 88.4% (95% CI: 67.1-95.9) in Eastern/Southeastern Asia, 79.6% (95% CI: 71.3-85.5) in Latin America and the Caribbean, 50.0% (95% CI: 34.4-61.9) in Southern Asia and 46.1% (95% CI: 29.1-59.1) in sub-Saharan Africa. Region-specific effectiveness followed a similar pattern. There was also evidence of vaccine efficacy against severe diarrhea and diarrheal hospitalizations.

CONCLUSION

Our findings confirm the protective efficacy and effectiveness of rotavirus vaccination against rotavirus diarrheal outcomes among children under 5 globally.

Effectiveness of rotavirus vaccines against rotavirus infection and hospitalization in Latin America: systematic review and meta-analysis

Background

Rotavirus was the leading cause of childhood diarrhoea-related hospitalisations and death before the introduction of rotavirus vaccines.

Methods

We describe the effectiveness of rotavirus vaccines to prevent rotavirus infections and hospitalizations and the main rotavirus strains circulating before and after vaccine introduction through a systematic review and meta-analysis of studies published between 1990 and 2014. 203 studies were included to estimate the proportion of infections due to rotavirus and 10 to assess the impact of the vaccines. 41 of 46 studies in the post-vaccination period were used for meta-analysis of genotypes, 20 to calculate VE against infection, eight for VE against hospitalisation and seven for VE against severe rotavirus-diarrhoea.

Results

24.3 % (95 % CI 22.1–26.5) and 16.1 % (95 % CI 13.2–19.3) of cases of diarrhoea were due to rotavirus before and after vaccine introduction, respectively. The most prevalent G types after vaccine introduction were G2 (51.6 %, 95 % CI 38–65), G9 (14.5 %, 95 % CI 7–23) and G1 (14.2 %, 95 % CI 7–23); while the most prevalent P types were P[4] (54.1 %, 95 % CI 41–67) and P[8] (33 %, 95 % CI 22–46). G2P[4] was the most frequent genotype combination after vaccine introduction. Effectiveness was 53 % (95 % CI 46–60) against infection, 73 % (95 % CI, 66–78) against hospitalisation and 74 % (95 % CI, 68.0–78.0) against severe diarrhoea. Reductions in hospitalisations and mortality due to diarrhoea were observed in countries that adopted universal rotavirus vaccination.

Conclusions

Rotavirus vaccines are effective in preventing rotavirus-diarrhoea in children in Latin America. The vaccines were associated with changes in genotype distribution.

Electronic supplementary material

The online version of this article (doi:10.1186/s40249-016-0173-2) contains supplementary material, which is available to authorized users.

Rotavirus epidemiology and surveillance before vaccine introduction in Argentina, 2012-2014

Group A Rotavirus has been widely described as one of the most important infantile diarrheal pathogens worldwide. In Argentina, it is responsible for over 200,000 acute diarrhea cases and from 30 to 50 deaths annually in children under 5 years. The aim of this study is to analyze frequency, seasonality, age group distribution, and circulating genotypes based on data notified in the 2012-2014 period and in turn to assess the pre-vaccine scenario, considering that rotavirus vaccine was introduced in 2015. Data were taken from the Viral Diarrhea Notification module of the Argentine SNVS-SIVILA surveillance tool. Analyses of circulating genotypes were performed on rotavirus-positive stool specimens by conventional binary characterization of the outermost capsid genes. Overall data showed rotavirus detection in about 25% of samples tested, and higher rates in children under 2 years old were observed. Rotavirus positive cases were distributed according to a typical winter seasonal pattern. A heterogeneous regional pattern of prevalence was also observed, with higher rates detected in the North region. Genotype co-circulation and annual fluctuation were observed. In general, G1P[8], G2P[4], G3P[8], and G12P[8] were the most frequently detected genotypes. This study represents the last survey taken of a population considered to be naïve. J. Med. Virol. 89:423-428, 2017. © 2016 Wiley Periodicals, Inc.

VP7 and VP8* genetic characterization of group A rotavirus genotype G12P[8]: Emergence and spreading in the Eastern Brazilian coast in 2014

Group A rotavirus (RVA) genotype G12 is habitually associated with diarrhea disease (DD) in African children and recently its detection has increased worldwide. A total of 970 stool samples collected from individuals with DD in the Northeastern, Southeastern, and Southern Brazilian regions, Eastern coast, were analyzed and 321 (33%) were positive for RVA and of these, 241 (75%) genotyped as G12P[8]. The rate of RVA positivity was higher among children aged 5-10 years old (60%). All RVA infections observed in adults aged >21 years were G12P[8] (n = 27) showing that this genotype affected older age groups during the year of 2014 in Brazil. Phylogenetic analysis of VP7 and VP8* G12P[8] strains demonstrated an elevated similarity among Brazilian and G12-III prototypes strains circulating worldwide recently, suggesting that this lineage is associated with the global spread of the G12 genotype, considered as the 6th most prevalent human RVA genotype nowadays; while other G12 lineages remain sporadically detected and usually detected in association with other P genotypes. VP8* analysis revealed that Brazilian strains belong to P[8]-3 lineage, the single P[8] lineage presently detected in the country. No major nucleotide/amino acid disparities were observed among strains recovered from children and adults for VP7 and VP8* genes. These data are essential to support the surveillance studies, particularly in countries where the RVA vaccine was introduced in their National Immunization Program enabling identification of potential alterations in the epidemiological profile that can impact its efficacy in vaccination programs. J. Med. Virol. 89:64-70, 2017. © 2016 Wiley Periodicals, Inc.

Managing Microbial Risks from Indirect Wastewater Reuse for Irrigation in Urbanizing Watersheds

Limited supply of clean water in urbanizing watersheds creates challenges for safely sustaining irrigated agriculture and global food security. On-farm interventions, such as riverbank filtration (RBF), are used in developing countries to treat irrigation water from rivers with extensive fecal contamination. Using a Bayesian approach incorporating ethnographic data and pathogen measurements, quantitative microbial risk assessment (QMRA) methods were employed to assess the impact of RBF on consumer health burdens for Giardia, Cryptosporidium, rotavirus, norovirus, and adenovirus infections resulting from indirect wastewater reuse, with lettuce irrigation in Bolivia as a model system. Concentrations of the microbial source tracking markers pepper mild mottle virus and HF183 Bacteroides were respectively 2.9 and 5.5 log10 units lower in RBF-treated water than in the river water. Consumption of lettuce irrigated with river water caused an estimated median health burden that represents 37% of Bolivia's overall diarrheal disease burden, but RBF resulted in an estimated health burden that is only 1.1% of this overall diarrheal disease burden. Variability and uncertainty associated with environmental and cultural factors affecting exposure correlated more with QMRA-predicted health outcomes than factors related to disease vulnerability. Policies governing simple on-farm interventions like RBF can be intermediary solutions for communities in urbanizing watersheds that currently lack wastewater treatment.

Probiotics, antibiotics and the immune responses to vaccines

Orally delivered vaccines have been shown to perform poorly in developing countries. There are marked differences in the structure and the luminal environment of the gut in developing countries resulting in changes in immune and barrier function. Recent studies using newly developed technology and analytic methods have made it increasingly clear that the intestinal microbiota activate a multitude of pathways that control innate and adaptive immunity in the gut. Several hypotheses have been proposed for the underperformance of oral vaccines in developing countries, and modulation of the intestinal microbiota is now being tested in human clinical trials. Supplementation with specific strains of probiotics has been shown to have modulatory effects on intestinal and systemic immune responses in animal models and forms the basis for human studies with vaccines. However, most studies published so far that have evaluated the immune response to vaccines in children and adults have been small and results have varied by age, antigen, type of antibody response and probiotic strain. Use of anthelminthic drugs in children has been shown to possibly increase immunogenicity following oral cholera vaccination, lending further support to the rationale for modulation of the immune response to oral vaccination through the intestinal microbiome.

Noninterference of Rotavirus Vaccine With Measles-Rubella Vaccine at 9 Months of Age and Improvements in Antirotavirus Immunity: A Randomized Trial

Background. The burden of rotavirus morbidity and mortality is high in children aged <5 years in developing countries, and evaluations indicate waning protection from rotavirus immunization in the second year. An additional dose of rotavirus vaccine may enhance the immune response and lengthen the period of protection against disease, but coadministration of this dose should not interfere with immune responses to concurrently given vaccines.

Methods. A total of 480 9-month-old participants from Matlab, Bangladesh, were enrolled in a study with a primary objective to establish noninferiority of concomitant administration of measles-rubella vaccine (MR) and a third dose of human rotavirus vaccine (HRV; MR + HRV), compared with MR given alone. Secondary objectives included noninferiority of rubella antibody seroconversion and evaluating rotavirus IgA/IgG seroresponses in MR + HRV recipients.

Results. Two months after vaccination, 75.3% and 74.3% of MR + HRV and MR recipients, respectively, had seroprotective levels of measles virus antibodies; 100.0% and 99.6%, respectively, showed anti–rubella virus immunoglobulin G (IgG) seroprotection. In the MR + HRV group, antirotavirus immunoglobulin A and IgG seropositivity frequencies before vaccination (52.7% and 66.3%, respectively) increased to 69.6% and 88.3% after vaccination.

Conclusions. Vaccine-induced measles and rubella antibody responses are not negatively affected by concomitant administration of HRV. The HRV dose increases antirotavirus serum antibody titers and the proportion of infants with detectable antirotavirus antibody.

Clinical Trials Registration. NCT01700621.

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.

Burden of Norovirus and Rotavirus in Children After Rotavirus Vaccine Introduction, Cochabamba, Bolivia

The effectiveness of rotavirus vaccine in the field may set the stage for a changing landscape of diarrheal illness affecting children worldwide. Norovirus and rotavirus are the two major viral enteropathogens of childhood. This study describes the prevalence of norovirus and rotavirus 2 years after widespread rotavirus vaccination in Cochabamba, Bolivia. Stool samples from hospitalized children with acute gastroenteritis (AGE) and outpatients aged 5-24 months without AGE were recruited from an urban hospital serving Bolivia's third largest city. Both viruses were genotyped, and norovirus GII.4 was further sequenced. Norovirus was found much more frequently than rotavirus. Norovirus was detected in 69/201 (34.3%) of specimens from children with AGE and 13/71 (18.3%) of those without diarrhea. Rotavirus was detected in 38/201 (18.9%) of diarrheal specimens and 3/71 (4.2%) of non-diarrheal specimens. Norovirus GII was identified in 97.8% of norovirus-positive samples; GII.4 was the most common genotype (71.4% of typed specimens). Rotavirus G3P[8] was the most prevalent rotavirus genotype (44.0% of typed specimens) and G2P[4] was second most prevalent (16.0% of typed specimens). This community is likely part of a trend toward norovirus predominance over rotavirus in children after widespread vaccination against rotavirus.

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.

Determination of a Viral Load Threshold To Distinguish Symptomatic versus Asymptomatic Rotavirus Infection in a High-Disease-Burden African Population

We evaluated quantitative real-time PCR to establish the diagnosis of rotavirus gastroenteritis in a high-disease-burden population in Malawi using enzyme immunoassay as the gold standard diagnostic test. In 146 children with acute gastroenteritis and 65 asymptomatic children, we defined a cutoff point in the threshold cycle value (26.7) that predicts rotavirus-attributable gastroenteritis in this population. These data will inform the evaluation of direct and indirect rotavirus vaccine effects in Africa.

Effect of monovalent rotavirus vaccine on rotavirus disease burden and circulating rotavirus strains among children in Morocco

Rotarix(TM) vaccine was introduced into the National Program of Immunization of Morocco in October 2010, reaching quickly 87% of the target population of children nationally. The incidence of rotavirus gastroenteritis and the prevalence of circulating rotavirus strains has been monitored in three sentinel hospitals since June 2006. The average percentage of rotavirus positive cases among all children under 5 years old hospitalized for gastroenteritis during the pre-vaccine period (2006-2010) was 44%. This percentage dropped to 29%, 15% and 24% in the 3 years post vaccine introduction (2011, 2012 and 2013), which is a decline of 34%, 66%, and 45%, respectively. Declines in prevalence were greatest among children 0-1 years of age (53%) and were most prominent during the winter and autumn rotavirus season. The prevalence of the G2P[4] and G9P[8] genotype sharply increased in the post vaccine period (2011-2013) compared to the previous seasons (2006-2010). Rotavirus vaccines have reduced greatly the number of children hospitalized due to rotavirus infection at the three sentinel hospitals; it is however unclear if the predominance of G2P[4] and G9P[8] genotypes is related to the vaccine introduction, or if this is attributable to normal genotype fluctuations. Continued surveillance will be pivotal to answer this question in the future.

Anticipating rotavirus vaccines--a pre-vaccine assessment of incidence and economic burden of rotavirus hospitalizations among children < 5 year of age in Libya, 2012-13

BACKGROUND

Libya introduced rotavirus vaccine in October 2013. We examined pre-vaccine incidence of rotavirus hospitalizations and associated economic burden among children < 5 years in Libya to provide baseline data for future vaccine impact evaluations.

METHODS

Prospective, hospital-based active surveillance for rotavirus was conducted at three public hospitals in two cities during August 2012 - April 2013. Clinical, demographic and estimated cost data were collected from children <5 hospitalized for diarrhea; stool specimens were tested for rotavirus with a commercial enzyme immunoassay. Annual rotavirus hospitalization incidence rate estimates included a conservative estimate based on the number of cases recorded during the nine months and an extrapolation to estimate 12 months incidence rate. National rotavirus disease and economic burden were estimated by extrapolating incidence and cost data to the national population of children aged < 5 years.

RESULTS

A total of 410 children < 5 years of age with diarrhea were enrolled, of whom 239 (58%) tested positive rotavirus, yielding an incidence range of 418-557 rotavirus hospitalizations per 100,000 children < 5 years of age. Most (86%) rotavirus cases were below two years of age with a distinct seasonal peak in winter (December-March) months. The total cost of treatment for each rotavirus patient was estimated at US$ 679 (range: 200-5,423). By extrapolation, we estimated 2,948 rotavirus hospitalizations occur each year in Libyan children < 5 years of age, incurring total costs of US$ 2,001,662 (range: 1,931,726-2,094,005).

CONCLUSIONS

Rotavirus incurs substantial morbidity and economic burden in Libya, highlighting the potential value of vaccination of Libyan children against rotavirus.