Heterogeneity of Rotavirus Vaccine Efficacy Among Infants in Developing Countries

Application of the cell-based RT-qPCR assay (C-QPA) for potency detection of the novel trivalent rotavirus vaccine in China

BACKGROUND

Because of the deficiencies of traditional methods in multivalent rotavirus vaccine potency detection, a cell-based quantitative RT-qPCR assay (C-QPA) was established and validated for specificity, precision, and accuracy.

METHODS

In order to further validate the robustness of this method in actual titer detection, the linear range and the practical application under different conditions were tested using monovalent and trivalent rotavirus samples and standards.

RESULTS

Results showed that the linear range was 2.0-6.5, 3.9-8.3, and 3.5-8.1 UI (unit of infectivity) for G2, G3, and G4, respectively. Besides, unknown sample with high titer exceeding the linear range can be calculated by dilution. The UIs of serotypes G2, G3, and G4 in monovalent and trivalent rotavirus samples showed a relative deviation ≤4.10%, and the monovalent samples of the same serotype with or without protective agents showed a relative deviation ≤4.28%; the coefficient of variation (CV) of at least 176 tests (548 individual runs) of 3 in vitro-transcribed RNA standards with certain concentrations was not higher than 6.50%; the results of the trivalent samples tested by more than 149 times in 5 years (467 individual runs) showed the CVs lower than 12.66%; 15 samples detected by one laboratory showed a CV lower than 9.83%, while other three samples tested by two independent laboratories showed a CV lower than 6.90%.

CONCLUSION

In summary, the C-QPA has good linearity, durability, repeatability, and reproducibility in practical application and has been proved by the authority to be widely used in the production, quality control and release of the recently licensed trivalent vaccine in China.

In Vitro Evaluation of Anti-Rotaviral Activity and Intestinal Toxicity of a Phytotherapeutic Prototype of Achyrocline bogotensis (Kunth) DC

Viruses represent the primary etiologic agents (70-80%) of acute diarrheal disease (ADD), and rotavirus (RV) is the most relevant one. Currently, four rotavirus vaccines are available. However, these vaccines do not protect against emerging viral strains or are not available in low-income countries. To date, there are no approved drugs available against rotavirus infection. In this study, we evaluated the in vitro anti-rotaviral activity and intestinal toxicity of a phytotherapeutic prototype obtained from Achyrocline bogotensis (Kunth) DC. (PPAb); medicinal plant that contains compounds that inhibit the rotavirus replication cycle. Virucidal and viral yield reduction effects exerted by the PPAb were evaluated by immunocytochemistry and flow cytometry. Furthermore, the toxic impact of the PPAb was evaluated in polarized human intestinal epithelial C2BBe1 cells in terms of cytotoxicity, loss of cytoplasmic membrane asymmetry, and DNA fragmentation by MTT and fluorometry. PPAb concentrations under 0.49 mg/mL exerted significant virucidal and viral yield reduction activities, and concentrations under 16 mg/mL neither reduced cell viability, produced DNA fragmentation, nor compromised the C2BBe1cell membrane stability after 24-h incubation. Based on these results, the evaluated phytotherapeutic prototype of Achyrocline bogotensis might be considered as a promising alternative to treat ADD caused by rotavirus.

Impact and effectiveness of monovalent rotavirus vaccine in Tajik children

BACKGROUND

In 2015, Tajikistan became the second country in Central Asia to introduce rotavirus vaccine into its national immunization program. Before vaccine introduction, rotavirus was estimated to cause > 40% of pediatric diarrhea hospitalizations in Tajikistan. We aimed to assess the impact of rotavirus vaccine introduction on rotavirus disease burden and estimate rotavirus vaccine effectiveness (VE).

METHODS

Using surveillance data from 2013 through 2019, we examined trends in monthly hospital admissions among children < 5 years old, before and after rotavirus vaccine introduction. Poisson regression was used to quantify decreases. VE was estimated using a test-negative case control design, with data from admissions during 2017 - 2019. Immunization records were obtained from clinics.

RESULTS

Among enrolled children, rotavirus positivity declined from 42% to 25% in the post-vaccine introduction period, a decrease of 41% (95% Confidence Interval [CI]: 36 - 45%). Declines were greatest in children < 12 months of age. Estimated VE of a complete course of rotavirus vaccine was 55% (95% CI: 21 - 73%) among children 5 - 59 months of age and 64% (95% CI: 36 - 80%) among children 5 - 23 months of age. VE point estimates were higher among children receiving both doses of rotavirus vaccine non-concurrently with OPV and among children receiving their first dose of rotavirus vaccine at 4 - 11 months of age, but CIs were wide and overlapping.

CONCLUSIONS

Our data demonstrate that rotavirus vaccine introduction was associated with a substantial reduction in pediatric rotavirus hospitalization burden in Tajikistan, and that rotavirus vaccination is effective in Tajik children.

Ethical considerations in international clinical trial site selection

New medicines and vaccines are predominantly tested in high-income countries. However, as the COVID-19 pandemic highlighted, the populations who can benefit from these interventions are not limited to these wealthier regions. One-third of novel Food and Drug Administration approved drugs, sponsored by large companies, treat infectious diseases like tuberculosis and HIV, which disproportionately affect low-income and middle-income countries (LMICs). The medicines for non-communicable diseases (NCDs) are also relevant to LMIC health needs, as over three-quarters of deaths from NCDs occur in LMICs. There are concerns clinical trial data may not extrapolate across geographical regions, as product effectiveness can vary substantially by region. The pentavalent rotavirus vaccine, for example, had markedly lower efficacy in LMICs. Efficacy variations have also been found for other vaccines and drugs. We argue there are strong ethical arguments for remedying some of this uneven distribution of clinical trial sites by geography and income. Chief among them, is that these disparities can impede equitable access to the benefits of clinical research, such as representation in the evidence base generated to guide prescribing and use of medicines and vaccines. We suggest trial site locations should be made more transparent and for later stage trials their selection should be informed by the global distribution of disease burden targeted by an experimental product. Countries with high prevalence, incidence, severity or infection transmission rates for targeted diseases should have real opportunities to engage in and enrol their populations in trials for novel medicines and vaccines.

Mucosal immunity to poliovirus

A cornerstone of the global initiative to eradicate polio is the widespread use of live and inactivated poliovirus vaccines in extensive public health campaigns designed to prevent the development of paralytic disease and interrupt transmission of the virus. Central to these efforts is the goal of inducing mucosal immunity able to limit virus replication in the intestine. Recent clinical trials have evaluated new combined regimens of poliovirus vaccines, and demonstrated clear differences in their ability to restrict virus shedding in stool after oral challenge with live virus. Analyses of mucosal immunity accompanying these trials support a critical role for enteric neutralizing IgA in limiting the magnitude and duration of virus shedding. This review summarizes key findings in vaccine-induced intestinal immunity to poliovirus in infants, older children, and adults. The impact of immunization on development and maintenance of protective immunity to poliovirus and the implications for global eradication are discussed.

TLR genetic variation is associated with Rotavirus-specific IgA seroconversion in South African Black infants after two doses of Rotarix vaccine

Live oral rotavirus vaccines have significantly reduced rotavirus-related diarrheal morbidity and mortality globally, but low efficacy of these vaccines is observed in low-income countries where disease burden is highest. The biological basis of rotavirus vaccine failure remains unknown but likely includes both microbial and host factors. We investigated associations between 19 candidate SNPs in the TLR3, TLR7, TLR8, DDX58 and IFIH1 genes that play a role in innate immunity, and seroconversion in Black South African infants after vaccination with Rotarix at 6 and 14 weeks of age. Rotavirus-specific IgA antibody titre was measured by ELISA before each vaccine dose and four weeks after the second dose, and seroconversion was defined as a four-fold or greater increase in IgA antibody titre at 18 weeks of age when compared to pre-vaccine titres. A total of 95/138 individuals seroconverted (68.8%) and seroconversion was significantly affected by birthweight (P = 0.010), pre-vaccine IgA and IgG titres (P = 0.0002 and P = 0.007 respectively). rs2159377 SNP in TLR8 was significantly associated with seroconversion in a univariate allelic model (P = 0.015) and was borderline significant in a multivariable logistic regression adjusted for birthweight and pre-vaccine titres (P = 0.071), although these values did not remain significant after Bonferroni correction. A haplotype of six SNPs on the X chromosome across TLR7 and TLR8, including rs179008 and rs5935438 minor alleles, was significantly associated with seroconversion in a univariate model (P = 0.042), but not in a multivariable model or after Bonferroni correction. Epistatic interaction between rs5743305 in TLR3 and rs55789327 in DDX58 was significantly associated with seroconversion (P = 0.034) but a genetic risk score constructed from all 19 minor alleles was not. Our results suggest that TLR variants may influence IgA antibody production and seroconversion to Rotarix vaccine in South Africans. Host genetic variation contributes to the varying immunogenicity of live oral rotavirus vaccines.

Vaccines for preventing rotavirus diarrhoea: vaccines in use

BACKGROUND

Rotavirus is a common cause of diarrhoea, diarrhoea-related hospital admissions, and diarrhoea-related deaths worldwide. Rotavirus vaccines prequalified by the World Health Organization (WHO) include Rotarix (GlaxoSmithKline), RotaTeq (Merck), and, more recently, Rotasiil (Serum Institute of India Ltd.), and Rotavac (Bharat Biotech Ltd.).

OBJECTIVES

To evaluate rotavirus vaccines prequalified by the WHO for their efficacy and safety in children.

SEARCH METHODS

On 30 November 2020, we searched PubMed, the Cochrane Infectious Diseases Group Specialized Register, CENTRAL (published in the Cochrane Library), Embase, LILACS, Science Citation Index Expanded, Social Sciences Citation Index, Conference Proceedings Citation Index-Science, Conference Proceedings Citation Index-Social Science & Humanities. We also searched the WHO ICTRP, ClinicalTrials.gov, clinical trial reports from manufacturers' websites, and reference lists of included studies, and relevant systematic reviews.

SELECTION CRITERIA

We selected randomized controlled trials (RCTs) conducted in children that compared rotavirus vaccines prequalified for use by the WHO with either placebo or no intervention.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial eligibility and assessed risk of bias. One author extracted data and a second author cross-checked them. We combined dichotomous data using the risk ratio (RR) and 95% confidence interval (CI). We stratified the analyses by under-five country mortality rate and used GRADE to evaluate evidence certainty.

MAIN RESULTS

Sixty trials met the inclusion criteria and enrolled a total of 228,233 participants. Thirty-six trials (119,114 participants) assessed Rotarix, 15 trials RotaTeq (88,934 participants), five trials Rotasiil (11,753 participants), and four trials Rotavac (8432 participants). Rotarix Infants vaccinated and followed up for the first year of life In low-mortality countries, Rotarix prevented 93% of severe rotavirus diarrhoea cases (14,976 participants, 4 trials; high-certainty evidence), and 52% of severe all-cause diarrhoea cases (3874 participants, 1 trial; moderate-certainty evidence).  In medium-mortality countries, Rotarix prevented 79% of severe rotavirus diarrhoea cases (31,671 participants, 4 trials; high-certainty evidence), and 36% of severe all-cause diarrhoea cases (26,479 participants, 2 trials; high-certainty evidence).  In high-mortality countries, Rotarix prevented 58% of severe rotavirus diarrhoea cases (15,882 participants, 4 trials; high-certainty evidence), and 27% of severe all-cause diarrhoea cases (5639 participants, 2 trials; high-certainty evidence). Children vaccinated and followed up for two years In low-mortality countries, Rotarix prevented 90% of severe rotavirus diarrhoea cases (18,145 participants, 6 trials; high-certainty evidence), and 51% of severe all-cause diarrhoea episodes (6269 participants, 2 trials; moderate-certainty evidence).   In medium-mortality countries, Rotarix prevented 77% of severe rotavirus diarrhoea cases (28,834 participants, 3 trials; high-certainty evidence), and 26% of severe all-cause diarrhoea cases (23,317 participants, 2 trials; moderate-certainty evidence).  In high-mortality countries, Rotarix prevented 35% of severe rotavirus diarrhoea cases (13,768 participants, 2 trials; moderate-certainty evidence), and 17% of severe all-cause diarrhoea cases (2764 participants, 1 trial; high-certainty evidence). RotaTeq Infants vaccinated and followed up for the first year of life In low-mortality countries, RotaTeq prevented 97% of severe rotavirus diarrhoea cases (5442 participants, 2 trials; high-certainty evidence).  In medium-mortality countries, RotaTeq prevented 79% of severe rotavirus diarrhoea cases (3863 participants, 1 trial; low-certainty evidence).  In high-mortality countries, RotaTeq prevented 57% of severe rotavirus diarrhoea cases (6775 participants, 2 trials; high-certainty evidence), but there is probably little or no difference between vaccine and placebo for severe all-cause diarrhoea (1 trial, 4085 participants; moderate-certainty evidence).  Children vaccinated and followed up for two years In low-mortality countries, RotaTeq prevented 96% of severe rotavirus diarrhoea cases (5442 participants, 2 trials; high-certainty evidence).  In medium-mortality countries, RotaTeq prevented 79% of severe rotavirus diarrhoea cases (3863 participants, 1 trial; low-certainty evidence).  In high-mortality countries, RotaTeq prevented 44% of severe rotavirus diarrhoea cases (6744 participants, 2 trials; high-certainty evidence), and 15% of severe all-cause diarrhoea cases (5977 participants, 2 trials; high-certainty evidence).  We did not identify RotaTeq studies reporting on severe all-cause diarrhoea in low- or medium-mortality countries. Rotasiil Rotasiil has not been assessed in any RCT in countries with low or medium child mortality. Infants vaccinated and followed up for the first year of life In high-mortality countries, Rotasiil prevented 48% of severe rotavirus diarrhoea cases (11,008 participants, 2 trials; high-certainty evidence), and resulted in little to no difference in severe all-cause diarrhoea cases (11,008 participants, 2 trials; high-certainty evidence). Children vaccinated and followed up for two years In high-mortality countries, Rotasiil prevented 44% of severe rotavirus diarrhoea cases (11,008 participants, 2 trials; high-certainty evidence), and resulted in little to no difference in severe all-cause diarrhoea cases (11,008 participants, 2 trials; high-certainty evidence). Rotavac Rotavac has not been assessed in any RCT in countries with low or medium child mortality.  Infants vaccinated and followed up for the first year of life In high-mortality countries, Rotavac prevented 57% of severe rotavirus diarrhoea cases (6799 participants, 1 trial; moderate-certainty evidence), and 16% of severe all-cause diarrhoea cases (6799 participants, 1 trial; moderate-certainty evidence). Children vaccinated and followed up for two years In high-mortality countries, Rotavac prevented 54% of severe rotavirus diarrhoea cases (6541 participants, 1 trial; moderate-certainty evidence); no Rotavac studies have reported on severe all-cause diarrhoea at two-years follow-up. Safety No increased risk of serious adverse events (SAEs) was detected with Rotarix (103,714 participants, 31 trials; high-certainty evidence), RotaTeq (82,502 participants, 14 trials; moderate to high-certainty evidence), Rotasiil (11,646 participants, 3 trials; high-certainty evidence), or Rotavac (8210 participants, 3 trials; moderate-certainty evidence). Deaths were infrequent and the analysis had insufficient evidence to show an effect on all-cause mortality. Intussusception was rare.  AUTHORS' CONCLUSIONS: Rotarix, RotaTeq, Rotasiil, and Rotavac prevent episodes of rotavirus diarrhoea. The relative effect estimate is smaller in high-mortality than in low-mortality countries, but more episodes are prevented in high-mortality settings as the baseline risk is higher. In high-mortality countries some results suggest lower efficacy in the second year. We found no increased risk of serious adverse events, including intussusception, from any of the prequalified rotavirus vaccines.

Combating Childhood Infections in LMICs: evaluating the contribution of Big Data Big data, biomarkers and proteomics: informing childhood diarrhoeal disease management in Low- and Middle-Income Countries

Despite efforts to reduce the global burden of childhood diarrhoea, 50% of all cases globally occur in children under five years in Low–Income and Middle- Income Countries (LMICs) and knowledge gaps remain regarding the aetiological diagnosis, introduction of diarrhoeal vaccines, and the role of environmental enteric dysfunction and severe acute malnutrition. Biomarkers may assist in understanding disease processes, from diagnostics, to management of childhood diarrhoea and the sequelae to vaccine development. Proteomics has the potential to assist in the identification of new biomarkers to understand the processes in the development of childhood diarrhoea and to aid in developing new vaccines. Centralised repositories that enable mining of large data sets to better characterise risk factors, the proteome of both the patient and the different diarrhoeal pathogens, and the environment, could inform patient management and vaccine development, providing a systems biological approach to address the burden of childhood diarrhoea in LMICs.

Rotavirus Infection, Illness, and Vaccine Performance in Malnourished Children: A Review of the Literature

Live, oral rotavirus vaccines are more effective at preventing rotavirus disease in countries with low child mortality compared with high child mortality. Among several hypotheses, poorer protection in malnourished children, who are more prevalent in countries with high child mortality, may partially explain this difference. We conducted a literature search to identify articles with a laboratory-confirmed rotavirus endpoint that evaluated differences by malnutrition status in rotavirus vaccine effectiveness and vaccine efficacy (VE) or the prevalence of rotavirus infection or illness among children <5 years old. We identified 7 analyses from 11 countries published from 2007 to 2019 that stratified rotavirus VE by malnutrition status. Among well-nourished children, VE point estimates ranged from 71% to 84% in observational studies and 26% to 61% in clinical trials. Among malnourished children, they ranged from -28% to 45% in observational studies and -3% to 61% in clinical trials. The relative difference between VE in well-nourished and malnourished children by length-for-age ranged from 37% to 64%, by weight-for-age ranged from 0% to 107%, and by weight-for-height ranged from -65% to 137%. We identified 3 cohort and 6 cross-sectional studies of natural rotavirus infection and illness and none reported that malnourished children were more susceptible to rotavirus infection or illness than well-nourished children. Overall, rotavirus vaccines may offer less protection to children with malnutrition than well-nourished children. As malnourished children often have worse outcomes from diarrhea, high rotavirus vaccine coverage and a better understanding of the performance of oral rotavirus vaccines in this population is important, though our finding that malnourished children may be less susceptible to rotavirus provides important context and information for vaccine evaluation design.

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.

Rotavirus vaccines performance: dynamic interdependence of host, pathogen and environment

INTRODUCTION

As of January 2021, rotavirus vaccination programs have been implemented in 109 countries and their use has resulted in a positive impact on rotavirus-related diarrheal hospitalizations and mortality in children below 5 years of age. Despite these successes, several countries in Africa and Asia where disease burden is high have not yet implemented rotavirus vaccination at all or at a scale sufficient enough to demonstrate impact. This could be, among other reasons, due to poor vaccine coverage and the modest levels of efficacy and effectiveness of the vaccines in these resource-limited settings.

AREAS COVERED

We review various factors related to the human host (malnutrition, maternally derived antibodies and breastfeeding, genetic factors, blood group, and co-administration with oral polio vaccine), rotavirus pathogen (force of infection, strain diversity and coinfections), and the environment (related to the human microbiome) which reflect complex and interconnected processes leading to diminished vaccine performance in resource-limited settings.

EXPERT OPINION

Addressing the limiting factors for vaccine efficacy is needed but likely to take a long time to be resolved. An immediate solution is to increase the immunization coverage to higher values generating an overall effect of adequate proportion of protected population to reduce the prevalence of rotavirus disease.

Force of infection: a determinant of vaccine efficacy?

Vaccine efficacy (VE) can vary in different settings. Of the many proposed setting-dependent determinants of VE, force of infection (FoI) stands out as one of the most direct, proximate, and actionable. As highlighted by the COVID-19 pandemic, modifying FoI through non-pharmaceutical interventions (NPIs) use can significantly contribute to controlling transmission and reducing disease incidence and severity absent highly effective pharmaceutical interventions, such as vaccines. Given that NPIs reduce the FoI, the question arises as to if and to what degree FoI, and by extension NPIs, can modify VE, and more practically, as vaccines become available for a pathogen, whether and which NPIs should continue to be used in conjunction with vaccines to optimize controlling transmission and reducing disease incidence and severity.

New Insights into the Immune System Using Dirty Mice

The mouse (Mus musculus) is the dominant organism used to investigate the mechanisms behind complex immunological responses because of their genetic similarity to humans and our ability to manipulate those genetics to understand downstream function. Indeed, our knowledge of immune system development, response to infection, and ways to therapeutically manipulate the immune response to combat disease were, in large part, delineated in the mouse. Despite the power of mouse-based immunology research, the translational efficacy of many new therapies from mouse to human is far from ideal. Recent data have highlighted how the naive, neonate-like immune system of specific pathogen-free mice differs dramatically in composition and function to mice living under barrier-free conditions (i.e., "dirty" mice). In this review, we discuss major findings to date and challenges faced when using dirty mice and specific areas of immunology research that may benefit from using animals with robust and varied microbial exposure.

Rotavirus A infection in children under five years old with a double health problem: undernutrition and diarrhoea - a cross-sectional study in four provinces of Mozambique

BACKGROUND

Mozambique has a high burden of group A rotavirus (RVA) infection and chronic undernutrition. This study aimed to determine the frequency and potential risk factors for RVA infection in undernourished children under 5 years old with diarrhoea in Mozambique.

METHODS

The analysis was conducted using data from March 2015 to December 2017, regarding children under 5 years old with at least one type of undernutrition. Anthropometric measures were used to calculate indices of weight-for-age, weight-for-height and height-for-age through the Z-Scores. RVA results were extracted from the National Diarrhoea Surveillance database. Descriptive statistics, chi-square test was used for qualitative variables and organized in contingency tables and 95% Confidence Intervals (CI) were considered for the calculation of RVA infection proportion and in the multiple logistic regression models to estimate the adjusted odds ratios (AOR).

RESULTS

Of the 842 undernourished children included in the analysis, 27.2% (95% CI: 24.3-30.3%) were positive for RVA. The rate of RVA infection was 42.7% (95% CI: 38.0-47.5%) in the pre-vaccine period, with great reduction to 12.2% (95% CI: 9.4-15.6%) in the post-vaccine period. Most of the RVA undernourished children had severe wasting (33.3%) and severe stunting (32.0%). The risk of infection was significantly high in children from 0 to 11 months (p-value < 0.001) when compared to the age group of 24-59 months. A higher proportion of RVA infection was detected in households with five or more members (p-value = 0.029). Similar proportions of RVA were observed in children fed only by breast milk (34.9%) and breast milk with formula (35.6%). A higher proportion of undernourished HIV-positive children co-infected with RVA (7.4%) was observed.

CONCLUSIONS

The frequency of RVA infection in undernourished children declined following the introduction of the vaccine in Mozambique. Beyond the temporal variation, Maputo province, age and crowded households were also associated to RVA infection. A high proportion of RVA infection was observed in children with severe wasting and a triple burden of disease: undernutrition, RVA and HIV, highlighting the need to conduct follow-up studies to understand the long-term impact of these conditions on children's development.

Establishment of a cell-based quantitative reverse transcription-polymerase chain reaction (RT-qPCR) assay for detection of multivalent rotavirus vaccine

Because of deficiencies of traditional potency tests in rotavirus detection, a one-step TaqMan probe-based quantitative reverse transcription-polymerase chain reaction (RT-qPCR) assay combined with cell-based method was established to determine the infectious potency of the target virus in multivalent live rotavirus vaccines in vitro. Series dilutions of rotavirus samples were inoculated into Vero cells and cultured for 24 hours. The cells were lysed and the potency was detected by RT-qPCR. The reference standards with a known titer (lgCCID50 /mL) were assayed in parallel, and the potencies of each sample were determined using parallel line method. The specificity, precision and accuracy of the assay were evaluated, respectively. The results showed that messenger RNA produced during rotavirus replication was the primary template of RT-qPCR and the primers and probes were specific to each strain. The coefficient of variation of different wells and different working days did not exceed 6% and the results of the assay were proved to be concordant with those of cell culture infective dose 50% with a relative deviation less than 5%. This assay is a more rapid, cost-effective and high-throughput way for detecting multivalent rotavirus vaccine, and will be a valuable tool in the quality control and stability monitoring of live multivalent rotavirus vaccine.

Impact of Helminth Infections during Pregnancy on Vaccine Immunogenicity in Gabonese Infants

Helminth infections are common in sub-Saharan Africa. Besides direct clinical effects, a bias towards a T helper type 2 (Th2) cell immune response is observed. The consequences of parasite infection during pregnancy for the mother and particularly for the fetus and the newborn can be severe and may include impaired immune response during acute infection and vaccination. Here, we present data of immune responses to vaccines given within the expanded program on immunization (EPI) of infants born to helminth infected or non-infected mothers. The study was conducted in Lambaréné and surroundings, Gabon. Maternal helminth infection was diagnosed microscopically using the Kato-Katz method for soil-transmitted helminths (STH), urine filtration for Schistosoma haematobium infections and the saponin-based method for filarial infections. Plasma antibody levels to different vaccine antigens were measured in mothers and their offspring by enzyme-linked immunosorbent assay (ELISA) at different timepoints. We found 42.3% of the mothers to be infected with at least one helminth species. Significantly lower anti-tetanus toxoid immunoglobulin (Ig) G was detected in the cord blood of infants born to helminth infected mothers. Following vaccination, immune responses of the infants to EPI vaccines were similar between the two groups at nine and 12 months. Even though infection with helminths is still common in pregnant women in Gabon, in our setting, there was no evidence seen for a substantial effect on infants’ immune responses to vaccines given as part of the EPI.

Predictors of oral rotavirus vaccine immunogenicity in rural Zimbabwean infants

BACKGROUND

Oral rotavirus vaccines (RVV) have poor immunogenicity in low-income countries, for reasons that remain unclear. This study identified the determinants of RVV immunogenicity among infants in rural Zimbabwe.

METHODS

Anti-rotavirus IgA titres were measured among a sub-group of infants enrolled in the Sanitation Hygiene Infant Nutrition Efficacy (SHINE) trial (NCT01824940). SHINE was a cluster-randomized trial of improved infant and young child feeding, and improved water, sanitation and hygiene (WASH) in two rural Zimbabwean districts. Infants received RVV as part of the national immunisation programme. Among HIV-unexposed infants in the non-WASH trial arms, we evaluated associations between potential risk factors (vaccine schedule and dose, maternal and infant nutritional status, infant diarrhoea, and household environment) and RVV immunogenicity (seroconversion, seropositivity and geometric mean titres) using multivariable regression.

RESULTS

Among 219 infants with seroconversion data, 43 (20%) successfully seroconverted and 176 (80%) failed to seroconvert to RVV. Seroconversion was positively associated with a higher length-for-age Z-score (LAZ) around the time of vaccination (adjusted RR 1.27 (95% CI 1.04, 1.55), P = 0.021), and negatively associated with concurrent OPV and RVV administration (adjusted RR 0.36 (0.19, 0.71), P = 0.003). Among 472 infants with post-vaccination titres, a higher LAZ score was associated with increased seropositivity (aRR 1.21 (95% CI 1.06, 1.38), P = 0.004), and higher birthweight was associated with increased IgA titres (0.45 (95%CI 0.18, 1.09) U/mL greater per 100 g gain in birthweight; P = 0.001).

CONCLUSIONS

Infant ponderal and linear growth were positively associated with RVV immunogenicity, while concurrent administration of OPV was negatively associated with RVV immunogenicity. Together, these findings suggest that improving foetal growth and separating RVV and OPV administration are plausible approaches to increasing RVV immunogenicity.

Vaccines for preventing rotavirus diarrhoea: vaccines in use

BACKGROUND

Rotavirus results in more diarrhoea-related deaths in children under five years than any other single agent in countries with high childhood mortality. It is also a common cause of diarrhoea-related hospital admissions in countries with low childhood mortality. Rotavirus vaccines that have been prequalified by the World Health Organization (WHO) include a monovalent vaccine (RV1; Rotarix, GlaxoSmithKline), a pentavalent vaccine (RV5; RotaTeq, Merck), and, more recently, another monovalent vaccine (Rotavac, Bharat Biotech).

OBJECTIVES

To evaluate rotavirus vaccines prequalified by the WHO (RV1, RV5, and Rotavac) for their efficacy and safety in children.

SEARCH METHODS

On 4 April 2018 we searched MEDLINE (via PubMed), the Cochrane Infectious Diseases Group Specialized Register, CENTRAL (published in the Cochrane Library), Embase, LILACS, and BIOSIS. We also searched the WHO ICTRP, ClinicalTrials.gov, clinical trial reports from manufacturers' websites, and reference lists of included studies and relevant systematic reviews.

SELECTION CRITERIA

We selected randomized controlled trials (RCTs) in children comparing rotavirus vaccines prequalified for use by the WHO versus placebo or no intervention.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial eligibility and assessed risks of bias. One review author extracted data and a second author cross-checked them. We combined dichotomous data using the risk ratio (RR) and 95% confidence interval (CI). We stratified the analysis by country mortality rate and used GRADE to evaluate evidence certainty.

MAIN RESULTS

Fifty-five trials met the inclusion criteria and enrolled a total of 216,480 participants. Thirty-six trials (119,114 participants) assessed RV1, 15 trials (88,934 participants) RV5, and four trials (8432 participants) Rotavac. RV1 Children vaccinated and followed up the first year of life In low-mortality countries, RV1 prevents 84% of severe rotavirus diarrhoea cases (RR 0.16, 95% CI 0.09 to 0.26; 43,779 participants, 7 trials; high-certainty evidence), and probably prevents 41% of cases of severe all-cause diarrhoea (RR 0.59, 95% CI 0.47 to 0.74; 28,051 participants, 3 trials; moderate-certainty evidence). In high-mortality countries, RV1 prevents 63% of severe rotavirus diarrhoea cases (RR 0.37, 95% CI 0.23 to 0.60; 6114 participants, 3 trials; high-certainty evidence), and 27% of severe all-cause diarrhoea cases (RR 0.73, 95% CI 0.56 to 0.95; 5639 participants, 2 trials; high-certainty evidence). Children vaccinated and followed up for two years In low-mortality countries, RV1 prevents 82% of severe rotavirus diarrhoea cases (RR 0.18, 95% CI 0.14 to 0.23; 36,002 participants, 9 trials; high-certainty evidence), and probably prevents 37% of severe all-cause diarrhoea episodes (rate ratio 0.63, 95% CI 0.56 to 0.71; 39,091 participants, 2 trials; moderate-certainty evidence). In high-mortality countries RV1 probably prevents 35% of severe rotavirus diarrhoea cases (RR 0.65, 95% CI 0.51 to 0.83; 13,768 participants, 2 trials; high-certainty evidence), and 17% of severe all-cause diarrhoea cases (RR 0.83, 95% CI 0.72 to 0.96; 2764 participants, 1 trial; moderate-certainty evidence). No increased risk of serious adverse events (SAE) was detected (RR 0.88 95% CI 0.83 to 0.93; high-certainty evidence). There were 30 cases of intussusception reported in 53,032 children after RV1 vaccination and 28 cases in 44,214 children after placebo or no intervention (RR 0.70, 95% CI 0.46 to 1.05; low-certainty evidence). RV5 Children vaccinated and followed up the first year of life In low-mortality countries, RV5 probably prevents 92% of severe rotavirus diarrhoea cases (RR 0.08, 95% CI 0.03 to 0.22; 4132 participants, 5 trials; moderate-certainty evidence). We did not identify studies reporting on severe all-cause diarrhoea in low-mortality countries. In high-mortality countries, RV5 prevents 57% of severe rotavirus diarrhoea (RR 0.43, 95% CI 0.29 to 0.62; 5916 participants, 2 trials; high-certainty evidence), but there is probably little or no difference between vaccine and placebo for severe all-cause diarrhoea (RR 0.80, 95% CI 0.58 to 1.11; 1 trial, 4085 participants; moderate-certainty evidence). Children vaccinated and followed up for two years In low-mortality countries, RV5 prevents 82% of severe rotavirus diarrhoea cases (RR 0.18, 95% CI 0.08 to 0.39; 7318 participants, 4 trials; moderate-certainty evidence). We did not identify studies reporting on severe all-cause diarrhoea in low-mortality countries. In high-mortality countries, RV5 prevents 41% of severe rotavirus diarrhoea cases (RR 0.59, 95% CI 0.43 to 0.82; 5885 participants, 2 trials; high-certainty evidence), and 15% of severe all-cause diarrhoea cases (RR 0.85, 95% CI 0.75 to 0.98; 5977 participants, 2 trials; high-certainty evidence). No increased risk of serious adverse events (SAE) was detected (RR 0.93 95% CI 0.86 to 1.01; moderate to high-certainty evidence). There were 16 cases of intussusception in 43,629 children after RV5 vaccination and 20 cases in 41,866 children after placebo (RR 0.77, 95% CI 0.41 to 1.45; low-certainty evidence). Rotavac Children vaccinated and followed up the first year of life Rotavac has not been assessed in any RCT in countries with low child mortality. In India, a high-mortality country, Rotavac probably prevents 57% of severe rotavirus diarrhoea cases (RR 0.43, 95% CI 0.30 to 0.60; 6799 participants, moderate-certainty evidence); the trial did not report on severe all-cause diarrhoea at one-year follow-up. Children vaccinated and followed up for two years Rotavac probably prevents 54% of severe rotavirus diarrhoea cases in India (RR 0.46, 95% CI 0.35 to 0.60; 6541 participants, 1 trial; moderate-certainty evidence), and 16% of severe all-cause diarrhoea cases (RR 0.84, 95% CI 0.71 to 0.98; 6799 participants, 1 trial; moderate-certainty evidence). No increased risk of serious adverse events (SAE) was detected (RR 0.93 95% CI 0.85 to 1.02; moderate-certainty evidence). There were eight cases of intussusception in 5764 children after Rotavac vaccination and three cases in 2818 children after placebo (RR 1.33, 95% CI 0.35 to 5.02; very low-certainty evidence). There was insufficient evidence of an effect on mortality from any rotavirus vaccine (198,381 participants, 44 trials; low- to very low-certainty evidence), as the trials were not powered to detect an effect at this endpoint.

AUTHORS' CONCLUSIONS

RV1, RV5, and Rotavac prevent episodes of rotavirus diarrhoea. Whilst the relative effect estimate is smaller in high-mortality than in low-mortality countries, there is a greater number of episodes prevented in these settings as the baseline risk is much higher. We found no increased risk of serious adverse events. 21 October 2019 Up to date All studies incorporated from most recent search All published trials found in the last search (4 Apr, 2018) were included and 15 ongoing studies are currently awaiting completion (see 'Characteristics of ongoing studies').

Vaccines for preventing rotavirus diarrhoea: vaccines in use

BACKGROUND

Rotavirus results in more diarrhoea-related deaths in children under five years than any other single agent in countries with high childhood mortality. It is also a common cause of diarrhoea-related hospital admissions in countries with low childhood mortality. Rotavirus vaccines that have been prequalified by the World Health Organization (WHO) include a monovalent vaccine (RV1; Rotarix, GlaxoSmithKline), a pentavalent vaccine (RV5; RotaTeq, Merck), and, more recently, another monovalent vaccine (Rotavac, Bharat Biotech).

OBJECTIVES

To evaluate rotavirus vaccines prequalified by the WHO (RV1, RV5, and Rotavac) for their efficacy and safety in children.

SEARCH METHODS

On 4 April 2018 we searched MEDLINE (via PubMed), the Cochrane Infectious Diseases Group Specialized Register, CENTRAL (published in the Cochrane Library), Embase, LILACS, and BIOSIS. We also searched the WHO ICTRP, ClinicalTrials.gov, clinical trial reports from manufacturers' websites, and reference lists of included studies and relevant systematic reviews.

SELECTION CRITERIA

We selected randomized controlled trials (RCTs) in children comparing rotavirus vaccines prequalified for use by the WHO versus placebo or no intervention.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial eligibility and assessed risks of bias. One review author extracted data and a second author cross-checked them. We combined dichotomous data using the risk ratio (RR) and 95% confidence interval (CI). We stratified the analysis by country mortality rate and used GRADE to evaluate evidence certainty.

MAIN RESULTS

Fifty-five trials met the inclusion criteria and enrolled a total of 216,480 participants. Thirty-six trials (119,114 participants) assessed RV1, 15 trials (88,934 participants) RV5, and four trials (8432 participants) Rotavac.RV1 Children vaccinated and followed up the first year of life In low-mortality countries, RV1 prevents 84% of severe rotavirus diarrhoea cases (RR 0.16, 95% CI 0.09 to 0.26; 43,779 participants, 7 trials; high-certainty evidence), and probably prevents 41% of cases of severe all-cause diarrhoea (RR 0.59, 95% CI 0.47 to 0.74; 28,051 participants, 3 trials; moderate-certainty evidence). In high-mortality countries, RV1 prevents 63% of severe rotavirus diarrhoea cases (RR 0.37, 95% CI 0.23 to 0.60; 6114 participants, 3 trials; high-certainty evidence), and 27% of severe all-cause diarrhoea cases (RR 0.73, 95% CI 0.56 to 0.95; 5639 participants, 2 trials; high-certainty evidence).Children vaccinated and followed up for two yearsIn low-mortality countries, RV1 prevents 82% of severe rotavirus diarrhoea cases (RR 0.18, 95% CI 0.14 to 0.23; 36,002 participants, 9 trials; high-certainty evidence), and probably prevents 37% of severe all-cause diarrhoea episodes (rate ratio 0.63, 95% CI 0.56 to 0.71; 39,091 participants, 2 trials; moderate-certainty evidence). In high-mortality countries RV1 probably prevents 35% of severe rotavirus diarrhoea cases (RR 0.65, 95% CI 0.51 to 0.83; 13,768 participants, 2 trials; high-certainty evidence), and 17% of severe all-cause diarrhoea cases (RR 0.83, 95% CI 0.72 to 0.96; 2764 participants, 1 trial; moderate-certainty evidence).No increased risk of serious adverse events (SAE) was detected (RR 0.88 95% CI 0.83 to 0.93; high-certainty evidence). There were 30 cases of intussusception reported in 53,032 children after RV1 vaccination and 28 cases in 44,214 children after placebo or no intervention (RR 0.70, 95% CI 0.46 to 1.05; low-certainty evidence).RV5 Children vaccinated and followed up the first year of life In low-mortality countries, RV5 probably prevents 92% of severe rotavirus diarrhoea cases (RR 0.08, 95% CI 0.03 to 0.22; 4132 participants, 5 trials; moderate-certainty evidence). We did not identify studies reporting on severe all-cause diarrhoea in low-mortality countries. In high-mortality countries, RV5 prevents 57% of severe rotavirus diarrhoea (RR 0.43, 95% CI 0.29 to 0.62; 5916 participants, 2 trials; high-certainty evidence), but there is probably little or no difference between vaccine and placebo for severe all-cause diarrhoea (RR 0.80, 95% CI 0.58 to 1.11; 1 trial, 4085 participants; moderate-certainty evidence).Children vaccinated and followed up for two yearsIn low-mortality countries, RV5 prevents 82% of severe rotavirus diarrhoea cases (RR 0.18, 95% CI 0.08 to 0.39; 7318 participants, 4 trials; moderate-certainty evidence). We did not identify studies reporting on severe all-cause diarrhoea in low-mortality countries. In high-mortality countries, RV5 prevents 41% of severe rotavirus diarrhoea cases (RR 0.59, 95% CI 0.43 to 0.82; 5885 participants, 2 trials; high-certainty evidence), and 15% of severe all-cause diarrhoea cases (RR 0.85, 95% CI 0.75 to 0.98; 5977 participants, 2 trials; high-certainty evidence).No increased risk of serious adverse events (SAE) was detected (RR 0.93 95% CI 0.86 to 1.01; moderate to high-certainty evidence). There were 16 cases of intussusception in 43,629 children after RV5 vaccination and 20 cases in 41,866 children after placebo (RR 0.77, 95% CI 0.41 to 1.45; low-certainty evidence).Rotavac Children vaccinated and followed up the first year of life Rotavac has not been assessed in any RCT in countries with low child mortality. In India, a high-mortality country, Rotavac probably prevents 57% of severe rotavirus diarrhoea cases (RR 0.43, 95% CI 0.30 to 0.60; 6799 participants, moderate-certainty evidence); the trial did not report on severe all-cause diarrhoea at one-year follow-up.Children vaccinated and followed up for two yearsRotavac probably prevents 54% of severe rotavirus diarrhoea cases in India (RR 0.46, 95% CI 0.35 to 0.60; 6541 participants, 1 trial; moderate-certainty evidence), and 16% of severe all-cause diarrhoea cases (RR 0.84, 95% CI 0.71 to 0.98; 6799 participants, 1 trial; moderate-certainty evidence).No increased risk of serious adverse events (SAE) was detected (RR 0.93 95% CI 0.85 to 1.02; moderate-certainty evidence). There were eight cases of intussusception in 5764 children after Rotavac vaccination and three cases in 2818 children after placebo (RR 1.33, 95% CI 0.35 to 5.02; very low-certainty evidence).There was insufficient evidence of an effect on mortality from any rotavirus vaccine (198,381 participants, 44 trials; low- to very low-certainty evidence), as the trials were not powered to detect an effect at this endpoint.

AUTHORS' CONCLUSIONS

RV1, RV5, and Rotavac prevent episodes of rotavirus diarrhoea. Whilst the relative effect estimate is smaller in high-mortality than in low-mortality countries, there is a greater number of episodes prevented in these settings as the baseline risk is much higher. We found no increased risk of serious adverse events.

Timing of Rotavirus Vaccine Doses and Severe Rotavirus Gastroenteritis Among Vaccinated Infants in Low- and Middle-income Countries

BACKGROUND

Altering rotavirus vaccine schedules may improve vaccine performance in low- and middle-income countries. We analyzed data from clinical trials of the monovalent (RV1) and pentavalent (RV5) rotavirus vaccines in low- and middle-income countries to understand the association between vaccine dose timing and severe rotavirus gastroenteritis incidence.

METHODS

We assessed the association between variations in rotavirus vaccine administration schedules and severe rotavirus gastroenteritis risk. We used the complement of the Kaplan-Meier survival estimator to estimate risk differences for different schedules. To adjust risk differences (RDs) for confounding, we calibrated estimates in the vaccinated arm using estimates from the placebo arm.

RESULTS

There were 3,114 and 7,341 children included from the RV1 and RV5 trials, respectively. The 18-month adjusted severe rotavirus gastroenteritis risk was 4.0% (95% confidence interval [CI] = 1.1, 7.1) higher for those receiving their first RV5 dose at <6 versus ≥6 weeks. For RV1, there was a 4.0% (95% CI = 0.0, 8.2) increase in 12-month adjusted risk for a 4- versus 6-week interval between doses. Further analysis revealed those receiving their first RV5 dose at 3-4 and 5-7 weeks had 2.9% (95% CI = 0.8, 5.3) and 1.3% (95% CI = -0.3, 3.0), respectively, higher risk compared with those at 9-12 weeks. Those receiving their first dose at 8 weeks had the lowest risk (RD: -2.6% [95% CI = -5.4, -0.1]) compared with those at 9-12 weeks.

CONCLUSIONS

A modest delay in rotavirus vaccination start and increase in interval between doses may be associated with lower severe rotavirus gastroenteritis risk in low- and middle-income countries.

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.

The Significance of the Intestinal Microbiome for Vaccinology: From Correlations to Therapeutic Applications

Despite unprecedented advances in understanding the intestinal microbiome, its potential to improve fields such as vaccinology has yet to be realized. This review briefly outlines the immunologic potential of the intestinal microbiome for vaccinology and highlights areas where the microbiome holds specific promise in vaccinology. Oral rotavirus vaccine effectiveness in low-income countries is used as a case study to describe how the intestinal microbiome may be employed to improve a vaccine's immunogenicity. A top-down, evidence-based approach is proposed to identify effective microbiota-based applications for vaccine improvement. Applying evidence from field studies in pertinent populations that correlate microbiome composition with vaccine effectiveness to appropriate experimental platforms will lead to the identification of safe, vaccine-supporting microbiota targets that are relevant to populations in need of improvement in vaccine-induced immunity.

Timing and predictors of severe rotavirus gastroenteritis among unvaccinated infants in low- and middle-income countries

Delays in rotavirus vaccine schedule could improve performance in low- and middle-income countries (LMICs). However, delaying the first dose could be detrimental if infants experience severe rotavirus gastroenteritis (RVGE) early in life. Our objective was to describe the timing and predictors of severe RVGE in unvaccinated children in LMICs. We analysed the placebo arms from two clinical trials (cohort 1: NCT00241644; cohort 2: NCT00362648). We estimated the rate, cumulative incidence (per 1000 infants) and age distribution of severe RVGE episodes. Cox proportional hazards models were used to estimate hazard ratios and 95% confidence intervals (CI) for the association between baseline factors and severe RVGE. Cumulative incidence at 6 months of age was 23/1000 (95% CI 15-30) in cohort 1 and 6/1000 (95% CI 3-8) in cohort 2. Early antibiotic use (compared with no use) was associated with 2.03 (95% CI 1.18-3.48) and 1.41 (95% CI 0.80-2.51) times the rate of severe RVGE in cohorts 1 and 2, respectively. The cumulative incidence of severe RVGE was low at 6 months of age, suggesting that a 4-week delay in the vaccination schedule may not result in a large number of severe RVGE episodes prior to vaccine receipt.

Rotavirus Infection in the Auckland Region After the Implementation of Universal Infant Rotavirus Vaccination: Impact on Hospitalizations and Laboratory Implications

BACKGROUND

In July 2014, New Zealand introduced universal infant vaccination with RotaTeq (Merk & Co.) administered as 3 doses at 6 weeks, 3 and 5 months of age. We sought to assess the impact of rotavirus vaccination on gastroenteritis (GE) hospitalizations in the greater Auckland region and analyze changes in rotavirus testing in the period around vaccine introduction.

METHODS

Hospitalizations, laboratory testing rates and methods were compared between the pre-vaccine period (2009-2013), post-vaccine period (January 2015 to December 2015) and year of vaccine introduction (2014).

RESULTS

There was a 68% decline in rotavirus hospitalizations of children <5 years of age after vaccine introduction (from 258/100,000 to 83/100,000) and a 17% decline in all-cause gastroenteritis admissions (from 1815/100,000 to 1293/100,000). Reductions were also seen in pediatric groups too old to have received vaccine. Despite these changes, rotavirus testing rates in our region remained static in the year after vaccine introduction compared with the 2 prior years, and after vaccine introduction, we observed a high rate of false positives 19/58 (33%) in patients with reactive rotavirus tests.

CONCLUSIONS

Rotavirus vaccine has had a significant early impact on gastroenteritis hospitalizations for children in the Auckland region. However, continued rotavirus testing at pre-vaccine rates risks generating false positive results. Laboratories and clinicians should consider reviewing their testing algorithms before vaccine introduction.

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.

Differences of Rotavirus Vaccine Effectiveness by Country: Likely Causes and Contributing Factors

Rotaviruses are a major cause of acute gastroenteritis in infants and young children worldwide and in many other mammalian and avian host species. Since 2006, two live-attenuated rotavirus vaccines, Rotarix^® and RotaTeq^®, have been licensed in >100 countries and are applied as part of extended program of vaccination (EPI) schemes of childhood vaccinations. Whereas the vaccines have been highly effective in high-income countries, they were shown to be considerably less potent in low- and middle-income countries. Rotavirus-associated disease was still the cause of death in >200,000 children of <5 years of age worldwide in 2013, and the mortality is concentrated in countries of sub-Saharan Africa and S.E. Asia. Various factors that have been identified or suggested as being involved in the differences of rotavirus vaccine effectiveness are reviewed here. Recognition of these factors will help to achieve gradual worldwide improvement of rotavirus vaccine effectiveness.

Postdose 3 G1 serum neutralizing antibody as correlate of protection for pentavalent rotavirus vaccine

Although clinical trials of the pentavalent rotavirus vaccine (RotaTeq®, RV5) have demonstrated efficacy against RV gastroenteritis (RGE) in low and high-income settings, a clear correlate of protection or a measure of immune response that could predict efficacy has yet to be identified. This is the first time that immunogenicity data with both serum neutralized antibody (SNA) titers and anti-RV IgA titers from several clinical efficacy trials were pooled to provide a unique context for evaluating the correlation between immunogenicity and RGE risk or efficacy of RV5. The correlation between immunogenicity and RGE risk is evaluated with data at the individual subject level. The analyses show that higher Postdose 3 (PD3) G1 SNA titers are associated with lower odds of contracting any RGE. The correlation between immunogenicity and efficacy is assessed using aggregated population level data, which shows higher efficacy associated with higher PD3 G1 SNA geometric mean titer (GMT) ratio (between RV5 and placebo) and PD3 serum anti-RV IgA GMT ratio. Among high-income countries, efficacy plateaus over the range of PD3 G1 SNA GMT ratios and PD3 serum anti-RV IgA GMT ratios. From both individual- and population-level analyses, PD3 G1 SNA titers correlated most closely with the RGE risk or efficacy for RV5.

Protein Malnutrition Modifies Innate Immunity and Gene Expression by Intestinal Epithelial Cells and Human Rotavirus Infection in Neonatal Gnotobiotic Pigs

Malnutrition and rotavirus infection, prevalent in developing countries, individually and in combination, affect the health of millions of children, compromising their immunity and increasing the rates of death from infectious diseases. However, the interactions between the two and their combined effects on immune and intestinal functions are poorly understood. We have established the first human infant microbiota-transplanted neonatal pig model of childhood malnutrition that reproduced the impaired immune, intestinal, and other physiological functions seen in malnourished children. This model can be used to evaluate relevant dietary and other health-promoting interventions. Our findings provide an explanation of why adequate nutrition alone may lack efficacy in malnourished children.

Malnutrition affects millions of children in developing countries, compromising immunity and contributing to increased rates of death from infectious diseases. Rotavirus is a major etiological agent of childhood diarrhea in developing countries, where malnutrition is prevalent. However, the interactions between the two and their combined effects on immune and intestinal functions are poorly understood. In this study, we used neonatal gnotobiotic (Gn) pigs transplanted with the fecal microbiota of a healthy 2-month-old infant (HIFM) and fed protein-deficient or -sufficient bovine milk diets. Protein deficiency induced hypoproteinemia, hypoalbuminemia, hypoglycemia, stunting, and generalized edema in Gn pigs, as observed in protein-malnourished children. Irrespective of the diet, human rotavirus (HRV) infection early, at HIFM posttransplantation day 3 (PTD3), resulted in adverse health effects and higher mortality rates (45 to 75%) than later HRV infection (PTD10). Protein malnutrition exacerbated HRV infection and affected the morphology and function of the small intestinal epithelial barrier. In pigs infected with HRV at PTD10, there was a uniform decrease in the function and/or frequencies of natural killer cells, plasmacytoid dendritic cells, and CD103⁺ and apoptotic mononuclear cells and altered gene expression profiles of intestinal epithelial cells (chromogranin A, mucin 2, proliferating cell nuclear antigen, SRY-Box 9, and villin). Thus, we have established the first HIFM-transplanted neonatal pig model that recapitulates major aspects of protein malnutrition in children and can be used to evaluate physiologically relevant interventions. Our findings provide an explanation of why nutrient-rich diets alone may lack efficacy in malnourished children.

IMPORTANCE Malnutrition and rotavirus infection, prevalent in developing countries, individually and in combination, affect the health of millions of children, compromising their immunity and increasing the rates of death from infectious diseases. However, the interactions between the two and their combined effects on immune and intestinal functions are poorly understood. We have established the first human infant microbiota-transplanted neonatal pig model of childhood malnutrition that reproduced the impaired immune, intestinal, and other physiological functions seen in malnourished children. This model can be used to evaluate relevant dietary and other health-promoting interventions. Our findings provide an explanation of why adequate nutrition alone may lack efficacy in malnourished children.