Strain diversity plays no major role in the varying efficacy of rotavirus vaccines: An overview

Immunogenicity of RV1 and RV5 vaccines administered in standard and interchangeable mixed schedules: a randomized, double-blind, non-inferiority clinical trial in Mexican infants

Introduction

Rotavirus-associated diarrheal diseases significantly burden healthcare systems, particularly affecting infants under five years. Both Rotarix™ (RV1) and RotaTeq™ (RV5) vaccines have been effective but have distinct application schedules and limited interchangeability data. This study aims to provide evidence on the immunogenicity, reactogenicity, and safety of mixed RV1-RV5 schedules compared to their standard counterparts.

Methods

This randomized, double-blind study evaluated the non-inferiority in terms of immunogenicity of mixed rotavirus vaccine schedules compared to standard RV1 and RV5 schedules in a cohort of 1,498 healthy infants aged 6 to 10 weeks. Participants were randomly assigned to one of seven groups receiving various combinations of RV1, and RV5. Standard RV1 and RV5 schedules served as controls of immunogenicity, reactogenicity, and safety analysis. IgA antibody levels were measured from blood samples collected before the first dose and one month after the third dose. Non-inferiority was concluded if the reduction in seroresponse rate in the mixed schemes, compared to the standard highest responding scheme, did not exceed the non-inferiority margin of -0.10. Reactogenicity traits and adverse events were monitored for 30 days after each vaccination and analyzed on the entire cohort.

Results

Out of the initial cohort, 1,365 infants completed the study. Immunogenicity analysis included 1,014 infants, considering IgA antibody titers ≥20 U/mL as seropositive. Mixed vaccine schedules demonstrated non-inferiority to standard schedules, with no significant differences in immunogenic response. Safety profiles were comparable across all groups, with no increased incidence of serious adverse events or intussusception.

Conclusion

The study confirms that mixed rotavirus vaccine schedules are non-inferior to standard RV1 and RV5 regimens in terms of immunogenicity and safety. This finding supports the flexibility of rotavirus vaccination strategies, particularly in contexts of vaccine shortage or logistic constraints. These results contribute to the global effort to optimize rotavirus vaccination programs for broader and more effective pediatric coverage.Clinical trial registration: ClinicalTrials.gov, NCT02193061.

Safety and immunogenicity of a plant-derived rotavirus-like particle vaccine in adults, toddlers and infants

BACKGROUND

This study is the first clinical trial for a parenteral non-replicating rotavirus vaccine developed using virus-like particle (VLP) technology.

METHODS

This open-labeled, randomized, placebo-controlled trial was conducted in two parts: Part A (a first-in-human study in Australian adults) and Part B (ascending dose and descending age in South African adults, toddlers and infants). In Part A, two cohorts of 10 adults were assigned to receive a single intramuscular injection of 1 of 2 escalating dose levels of the rotavirus VLP (Ro-VLP) vaccine (7 μg or 21 μg) or placebo. In Part B, one cohort of 10 adults was assigned to receive a single injection of the Ro-VLP vaccine (21 μg) or placebo, two cohorts of 10 toddlers were assigned to receive 2 injections of 1 of 2 escalating dose levels of the Ro-VLP vaccine (7 μg or 21 μg) or placebo 28 days apart, and three cohorts of 20 infants were assigned to receive 3 injections of 1 of 3 escalating dose levels of the Ro-VLP vaccine (2.5 μg, 7 μg or 21 μg) or placebo or 2 doses of oral Rotarix 28 days apart. Safety, reactogenicity and immunogenicity were assessed.

RESULTS

There were no safety or tolerability concerns after administration of the Ro-VLP vaccine. The Ro-VLP vaccine induced an anti-G1P[8] IgG response in infants 4 weeks after the second and third doses. Neutralizing antibody responses against homologous G1P[8] rotavirus were higher in all Ro-VLP infant groups than in the placebo group 4 weeks after the third dose. No heterotypic immunity was elicited by the Ro-VLP vaccine.

CONCLUSIONS

The Ro-VLP vaccine was well tolerated and induced a homotypic immune response in infants, suggesting that this technology platform is a favorable approach for a parenteral non-replicating rotavirus vaccine.

CLINICAL TRIAL REGISTRATION

NCT03507738.

Economic evaluation of rotavirus vaccination: an important step of the introduction to the national immunization program in Thailand

INTRODUCTION

World Health Organization recommends rotavirus vaccine for all national immunization programs (NIPs). To provide country-specific evidence, we conducted economic evaluation of a monovalent rotavirus vaccination using specific data of the pilot phase in Thailand.

METHOD

A Markov model was adopted to compare the 2020 birth cohort once receiving rotavirus vaccination versus no vaccination from healthcare and societal perspective over five years. Data on disease burden, vaccine effectiveness, costs, and utilities were taken from a cohort study in two provinces of Thailand.  Sensitivity analyses were performed to test the robustness of the results.

RESULTS

Rotavirus vaccination would reduce rotavirus diarrhea and costs of illness by 48% and 71%, respectively, over the first five years of life. At USD 13 per dose, vaccine was cost-effective with the ICERs of USD 4,114 and USD 1,571per QALY gained from healthcare and societal perspective, respectively. Results were sensitive to incidence and vaccine cost.  The budget for vaccine purchasing was estimated at USD13 million per year.

CONCLUSION

Incorporating rotavirus vaccination into the NIP substantially reduced health and cost outcomes and was cost-effective for both perspectives. However, the government needs to negotiate vaccine price prior to program implementation to achieve favorable budget impact.

New approach of genetic characterization of group A rotaviruses by the nanopore sequencing method

Nanopore sequencing of virus genomes represented by segmented RNA (e.g. rotaviruses) requires the development of specific approaches. Due to the massive use of rotavirus vaccines, the relevance of monitoring the genetic diversity of circulating strains of group A rotaviruses (RVA) increased. The WHO recommended method of multiplex type-specific PCR does not allow genotyping of all clinically significant strains of RVA and identifying inter-strain differences within the genotype. We have described a new principle of amplification of RVA gene segments using six primers for reverse transcription and one universal primer for PCR for nanopore sequencing. The amplification of RVA genome was tested on clinical samples and three phylogenetically distant laboratory RVA strains, Wa (G1P[8]), DS-1 (G2P[4]) and 568 (G3P[3]). The developed protocol of sample preparation and nanopore sequencing allowed obtaining full-length sequences for gene segments of RVA, including the diagnostically significant segments 9 (VP7), 4 (VP4) and 6 (VP6) with high accuracy and coverage. The accuracy of sequencing of the rotavirus genome exceeded 99.5 %, and the genome coverage varied for different strains from 59.0 to 99.6 % (on average 86 %). The developed approach of nanopore sequencing of RVA genome could be a prospective tool for epidemiological studies and surveillance of rotavirus infection.

Rotavirus Genotypes in Hospitalized Children with Acute Gastroenteritis Before and After Rotavirus Vaccine Introduction in Blantyre, Malawi, 1997 - 2019

Background

Rotavirus vaccine (Rotarix [RV1]) has reduced diarrhea-associated hospitalizations and deaths in Malawi. We examined the trends in circulating rotavirus genotypes in Malawi over a 22-year period to assess the impact of RV1 introduction on strain distribution.

Methods

Data on rotavirus-positive stool specimens among children aged <5 years hospitalized with diarrhea in Blantyre, Malawi before (July 1997–October 2012, n = 1765) and after (November 2012–October 2019, n = 934) RV1 introduction were analyzed. Rotavirus G and P genotypes were assigned using reverse-transcription polymerase chain reaction.

Results

A rich rotavirus strain diversity circulated throughout the 22-year period; Shannon (H′) and Simpson diversity (D′) indices did not differ between the pre- and postvaccine periods (H′ P < .149; D′ P < .287). Overall, G1 (n = 268/924 [28.7%]), G2 (n = 308/924 [33.0%]), G3 (n = 72/924 [7.7%]), and G12 (n = 109/924 [11.8%]) were the most prevalent genotypes identified following RV1 introduction. The prevalence of G1P[8] and G2P[4] genotypes declined each successive year following RV1 introduction, and were not detected after 2018. Genotype G3 reemerged and became the predominant genotype from 2017 onward. No evidence of genotype selection was observed 7 years post–RV1 introduction.

Conclusions

Rotavirus strain diversity and genotype variation in Malawi are likely driven by natural mechanisms rather than vaccine pressure.

G2P[4] rotavirus outbreak in Belu, East Nusa Tenggara Province, Indonesia, 2018

Rotavirus is a major cause of acute gastroenteritis (AGE) in children worldwide. However, rotavirus outbreak has rarely been reported in Indonesia. This study aims to identify the causative agent for AGE outbreak among children in Belu, East Nusa Tenggara, Indonesia in 2018. All the samples were negative for bacteria (Salmonella, V. cholera) and Norovirus. Ten out of 11 stool samples were rotavirus-positive by immunochromatography testing. Reverse-transcription polymerase chain reaction (RT-PCR) and phylogenetic analyses revealed that rotavirus G2P[4] was the possible causative agent for the AGE outbreak, although sample size was limited. These findings suggest that the AGE outbreak was caused by rotavirus G2P[4], highlighting the importance of rotavirus surveillance.

VP7 and VP4 genotypes of rotaviruses cocirculating in Iran, 2015 to 2017: Comparison with cogent sequences of Rotarix and RotaTeq vaccine strains before their use for universal mass vaccination

The present study was conducted to analyze the genotypic diversity of circulating species A rotavirus (RVA) strains in Iran and also to investigate comparative analysis between the genotypes of VP4 and VP7 of cocirculating RVA and vaccine strains before the vaccine is introduced in the national immunization program. The G3-lineage I was found in this study as the most common G genotype which was followed by G9-lineage III, G1-lineages I, II, G12-lineage III, G2-lineage IV, and G4-lineage I. Also, P[8]-lineages III, IV was found as the predominant P genotype which was followed by P[4]-lineage V, and P[6]-lineage I. Overally, G3P[8] was determined as the most common combination. Moreover, the analysis of the VP7 antigenic epitopes showed that several amino acid differences existed between circulating Iranian and the vaccine strains. The comparison of genotype G1 of Iranian and vaccine strains (RotaTeq and Rotarix), and genotypes G2, G3, and G4 of Iranian and RotaTeq vaccine strains revealed three to five amino acids differences on the VP7 antigenic epitopes. Furthermore, analyzing of the VP8* epitopes of Iranian P[8] strains indicated that they contained up to 11 and 14 amino acid differences with Rotarix and RotaTeq, respectively. Based on different patterns of amino acid substitutions in circulating and vaccine strains, the emergence of antibody escaping mutants and potentially the decrease of immune protection might ensue in vaccinated children. However, considering the broad cross-protective activity of RVA vaccines, their efficacy should be monitored after the introduction in Iran.

Evolution of P[8], P[4], and P[6] VP8* genes of human rotaviruses globally reported during 1974 and 2017: possible implications for rotavirus vaccines in development

Non-replicating parenteral rotavirus (RV) vaccine candidates are in development in an attempt to overcome the lower efficacy and effectiveness of oral RV vaccines in low-income countries. One of the leading candidates is a truncated recombinant VP8* protein, expressed in Escherichia coli from original sequences of the prototype RV genotypes P[8], P[4], or P[6] isolated before 1983. Since VP8* is highly variable, it was considered useful to examine the evolutionary changes of RV strains reported worldwide over time in relation to the three P2-VP8 vaccine strains. Here, we retrieved from the GenBank 6,366 RV VP8* gene sequences of P[8], P[4], or P[6] strains isolated between 1974 and 2017, in 77 countries, and compared them with those of the three P2-VP8 vaccine strains: Wa (USA, 1974, G1P[8]), DS-1 (USA, 1976, G2P[4]), and 1076 (Sweden, 1983, G2P[6]). Phylogenetic analysis showed that 94.9% (4,328/4,560), 99.8% (1,141/1,143), and 100% (663/663) of the P[8], P[4], and P[6] strains, respectively, reported globally between 1974 and 2018 belong to non-vaccine lineages. These P[8], P[4], and P[6] RV strains have a mean of 9%, 5%, and 6% amino acid difference from the corresponding vaccine strains. Additionally, in the USA, the mean percentage difference between all the P[8] RV strains and the original Wa strain increased over time: 4% (during 1974-1980), 5% (1988-1991), and 9% (2005-2013). Our analysis substantiated high evolutionary changes in VP8* of the P[8], P[4], and P[6] major RV strains and their increasing variations from the candidate subunit vaccine strains over time. These findings may have implications for the development of new RV vaccines.

Environmental enteric dysfunction and growth

OBJECTIVE

To describe the current indicators of environmental enteric dysfunction and its association with linear growth deficit and the height-for-age anthropometric indicator.

DATA SOURCES

Narrative review with articles identified in PubMed and Scopus databases using combinations of the following words: environmental, enteric, dysfunction, enteropathy, and growth, as well as the authors' personal records.

DATA SYNTHESIS

In the last 15 years, new non-invasive markers have been investigated to characterize environmental enteric dysfunction; however, the best tests to be used have not yet been identified. There is evidence that, in environmental enteric dysfunction, a systemic inflammatory process may also occur as a consequence of increased intestinal permeability, in addition to intestinal mucosa abnormalities. Bacterial overgrowth in the small intestine and changes in fecal microbiota profile have also been identified. There is evidence indicating that environmental enteric dysfunction can impair not only full growth but also the neuropsychomotor development and response to orally administered vaccines. It is important to emphasize that the environmental enteric dysfunction is not a justification for not carrying out vaccination, which must follow the regular schedule. Another aspect to emphasize is the greater risk for those children who had height impairment in early childhood, possibly associated with environmental enteric dysfunction, to present overweight and obesity in adulthood when exposed to a high calorie diet, which has been called "triple burden."

CONCLUSIONS

According to the analyzed evidence, the control of environmental enteric dysfunction is very important for the full expression of growth, development, and vaccine response in the pediatric age group.

Would immunization be the same without cross-reactivity?

"Cross-reactivity" (the observed immune response against pathogen types not specifically targeted by the vaccine antigen composition) and "cross-protection" (clinical protection against related non-vaccine microorganism types) are vaccinology concepts that are attracting renewed interest in the context of disease prevention. National health authorities are collecting mounting evidence of the importance of cross-reactivity. For some vaccines, this has been substantiated by cross-protection data from clinical studies and/or post-licensure data, where their introduction into immunization programmes has shown beneficial impacts on disease caused by related non-vaccine microorganisms. This knowledge has influenced the way new vaccines are designed, developed, and evaluated in real-life settings. Some of the new vaccines are now designed with the specific aim of having a greater breadth of protection. Ideal vaccine antigens therefore include epitopes with conserved homology across related pathogen types, because it is not always possible to include the antigens of all the individual types of a given pathogen species. The use of novel adjuvants with greater immunostimulatory properties can also contribute to improved overall vaccine cross-reactivity, as could the use of antigen delivery platforms. The growing body of evidence allows us to better understand the full impact of vaccines - beyond vaccine-type disease - which should be taken into consideration when assessing the full value of vaccination programmes.

Therapeutics and Immunoprophylaxis Against Noroviruses and Rotaviruses: The Past, Present, and Future

Background:

Noroviruses and rotaviruses are important viral etiologies of severe gastroenteritis. Noroviruses are the primary cause of nonbacterial diarrheal outbreaks in humans, whilst rotaviruses are a major cause of childhood diarrhea. Although both enteric pathogens substantially impact human health and economies, there are no approved drugs against noroviruses and rotaviruses so far. On the other hand, whilst the currently licensed rotavirus vaccines have been successfully implemented in over 100 countries, the most advanced norovirus vaccine has recently completed phase-I and II trials.

Methods:

We performed a structured search of bibliographic databases for peer-reviewed research litera-ture on advances in the fields of norovirus and rotavirus therapeutics and immunoprophylaxis.

Results:

Technological advances coupled with a proper understanding of viral morphology and replication over the past decade has facilitated pioneering research on therapeutics and immunoprophylaxis against noroviruses and rotaviruses, with promising outcomes in human clinical trials of some of the drugs and vaccines. This review focuses on the various developments in the fields of norovirus and rotavirus thera-peutics and immunoprophylaxis, such as potential antiviral drug molecules, passive immunotherapies (oral human immunoglobulins, egg yolk and bovine colostral antibodies, llama-derived nanobodies, and anti-bodies expressed in probiotics, plants, rice grains and insect larvae), immune system modulators, probiot-ics, phytochemicals and other biological substances such as bovine milk proteins, therapeutic nanoparti-cles, hydrogels and viscogens, conventional viral vaccines (live and inactivated whole virus vaccines), and genetically engineered viral vaccines (reassortant viral particles, virus-like particles (VLPs) and other sub-unit recombinant vaccines including multi-valent viral vaccines, edible plant vaccines, and encapsulated viral particles).

Conclusions:

This review provides important insights into the various approaches to therapeutics and im-munoprophylaxis against noroviruses and rotaviruses..

A Multiplex PCR/LDR Assay for Viral Agents of Diarrhea with the Capacity to Genotype Rotavirus

Rotavirus and noroviruses are major causes of diarrhea. Variable rotavirus vaccination efficacy in Africa and Asia is multifactorial, including the diversity of circulating strains and viral co-infection. We describe a multiplexed assay that detects and genotypes viruses from stool specimens. It includes a one-step reverse transcriptase PCR reaction, a ligase detection reaction (LDR), then hybridization of fluorescent products to micro-beads. In clinical samples it detects rotavirus, caliciviruses (sapovirus and norovirus), mixed infections, and genotypes or genogroups of rotaviruses and noroviruses, respectively. The assay also has the capacity to detect hepatitis A. The assay was validated on reference isolates and 296 stool specimens from the US and Ghana. The assay was 97% sensitive and 100% specific. The genogroup was concordant in 100% of norovirus, and the genotype in 91% and 89% of rotavirus G- and P-types, respectively. Two rare rotavirus strains, G6P[6] and G6P[8], were detected in stool specimens from Ghana. The high-throughput assay is sensitive, specific, and may be of utility in the epidemiological surveillance for rare and emerging viral strains post-rotavirus vaccine implementation.

Molecular-Genetic Characterization of Human Rotavirus A Strains Circulating in Moscow, Russia (2009-2014)

Enteric viruses are the most common cause of acute gastroenteritis (AGE) in young children and a significant public health problem globally. Hospital admissions of children under 5 years of age with diarrhea are primarily associated with group A rotavirus (RVA) infection. In this retrospective study, the population structure of viruses linked to AGE etiology in young children hospitalized with AGE in Moscow was evaluated, and molecular characterization of RVA strains was performed. Fecal specimens were collected from children under 5 years old hospitalized with AGE between 2009 and 2014 in Moscow, Russia. Multiplex real-time reverse transcription PCR was used to detect enteric viruses and for G/[P]-genotyping of isolated RVAs. Sequencing of RVA VP7 and VP4 cDNA fragments was used to validate the data obtained by PCR-genotyping. The main causes for hospitalization of children with AGE were RVA (40.1%), followed by noroviruses (11.4%), while adenoviruses, astroviruses, sapoviruses, enteroviruses, and orthoreoviruses were detected in 4.7%, 1.9%, 1.4%, 1.2%, and 0.2% of samples tested, respectively. Nosocomial infections, predominantly associated with RVAs and noroviruses, were detected in 24.8% of cases and occurred significantly more frequently in younger infants. The predominant RVA genotype was G4P[8], detected in 38.7% of RVA-positive cases, whereas genotypes G1P[8], G9P[8], G3P[8], and G2P[4] were found in 11.8%, 6.6%, 4.2%, and 3.3% of cases, respectively. Together, the presence of circulating RVA strains with rare VP7 and VP4 gene variants (G6 and P[9]) highlights the need to conduct continuous epidemiological monitoring of RVA infection.

Rotavirus genotypes circulating in Ontario, Canada, before and after implementation of the rotavirus immunization program

BACKGROUND AND OBJECTIVES

Ontario introduced a universal publicly-funded group A rotavirus (RVA) immunization program in August 2011, using monovalent vaccine. RVA immunization programs have decreased the incidence of RVA acute gastroenteritis in many countries but it is unclear if it will contribute to the emergence of certain genotypes. We monitored RVA trends and genotypes in Ontario before and after implementation of the publicly-funded immunization program.

METHODS

RVA detection was conducted at Public Health Ontario Laboratories from January 2009 to December 2011 (pre-program period) and January 2012 to October 2015 (publicly-funded RVA immunization program period) and number of RVA-positive specimens and percent positivity were analysed. A convenience sample of RVA-positive stool specimens, from September 2010 to December 2011 (pre-program period) and January 2012 to June 2013 (program period), were genotyped using heminested PCR. A literature review on the burden of illness from emergent genotype was performed.

RESULTS

Stool specimens showed a significant decrease in RVA percent positivity from the 36 month pre-program period (14.4%; 1537/10700) to the 46 month program period (6.1%; 548/9019). An increase in the proportion of RVA G10 among genotyped specimens, associated with five different P genotypes, from the pre-program (6.3%; 13/205) to the program (31.5%; 40/127) period was observed. Our literature review identified approximately 200 G10-positive human stool specimens from 16 different countries.

CONCLUSIONS

This study documented a decrease in the number of RVA-positive specimens and percent positivity after implementation of the immunization program. An unexpected increase in the proportion of RVA G10 was detected following program introduction. Ongoing RVA surveillance is important in evaluating both the long-term impact of immunization and emergence of RVA genotypes.

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.

Pre-vaccine circulating group a rotavirus strains in under 5 years children with acute diarrhea during 1999-2013 in Cameroon

The aim of this review was to assess all the studies on rotavirus G and P characterization during the pre-vaccine period (1999-2013) in Cameroon to have a better basis for post-vaccine introduction evaluations. A retrospective study was done through a comprehensive review of published (PubMed, Google Scholar) and accessible unpublished data on rotavirus G and P genotypes circulating in five regions of Cameroon. Descriptive data were expressed as frequencies tables and proportions. A total of 1844 rotavirus positive cases were analyzed. In all, 1534 strains were characterized for the P (VP4) specificity. Six different VP4 genotypes were observed, including P [4], P [6], P [8], P [9], P [10] and P [14]. The most predominant P genotypes were P [8] at 42.6%, and P [6] at 37.9%. Mixed infections were observed at 5.3%, whereas 4.1% of the strains were P non-typeable. A total of 1518 rotavirus strains were characterized for the G (VP7) specificity. VP7 genotypes G1, G2, G3, G4, G5, G6, G8, G9, G10 and G12 were observed. G1 (35.3%), G3 (19.5%), G2 (14.9%) and G12 (10.1%) were the predominant G genotypes while G5 and G10 were least prevalent at 0.06% each. Approximately 5.1% of all strains were G non-typeable whereas 5.3% were mixed G genotypes. A total of 1472 strains were characterized for both G and P genes, from which 38 different G-P combinations were observed. Overall, G1P [8] (22%) was identified as the predominant rotavirus strain circulating in Cameroon followed by G3P [6] (15%). In conclusion, we observed that the genotypes identified in Cameroon during 1999-2013 were partially covered by the two WHO recommended rotavirus vaccines. This review provides comprehensive up-to-date information on rotavirus strain surveillance in Cameroon during the pre-vaccination era.

Characterization of rotavirus infection in children with acute gastroenteritis in Bengo province, Northwestern Angola, prior to vaccine introduction

BACKGROUND

Rotavirus group A (RVA) is considered the leading cause of pediatric diarrhea, responsible for the high burden of diarrheal diseases in sub-Saharan Africa. Despite recent studies, the existent data are scarce for some African countries like Angola, a country with one of the highest RVA-related death estimates. The aim of this study was to determine the RVA detection rate and circulating genotypes in children less than five years of age with acute gastroenteritis attended at the Bengo General Hospital in Caxito, Bengo province, Angola, before vaccine introduction.

METHODS

Between September 2012 and December 2013, 342 fecal specimens were collected from children enrolled. Positive samples for RVA by immunochromatographic rapid test were G and P-typed by hemi-nested type-specific multiplex PCR, and subgrouped for the VP6 gene. VP4 and VP7 genes from a subset of samples were sequenced for phylogenetic analysis.

RESULTS

During the study period, a high RVA detection rate was registered (25.1%, 86/342). The age group most affected by RVA infection includes children under 6 months of age (p<0.01). Vomiting was highly associated with RVA infection (72.1%; p<0.001). From the 86 RVA-positive samples, 72 (83.7%) were genotyped. The most prevalent genotype was G1P[8] (34/72; 47.2%), followed by the uncommon G1P[6] (21/72; 29.2%), and G2P[4] (9/72; 12.5%). Only two G-types were found: G1 (60/72; 83.3%) and G2 (11/72; 15.3%). Among the P-genotypes, P[8] was the most prevalent (34/72; 47.2%), followed by P[6] (22/72; 30.6%) and P[4] (9/72; 12.5%). In the phylogenetic trees, the identified G and P-types clustered tightly together and with reference sequences in specific monophyletic groups, with highly significant bootstrap values (≥92%).

CONCLUSION

This pre-vaccination study revealed, for the first time for Bengo province (Angola), the RVA genotype profile, including phylogenetic relationships, and a high RVA detection rate, supporting the immediate introduction of a RVA vaccine in the national immunization programme.

Comparative analysis of the immunogenicity of monovalent and multivalent rotavirus immunogens

The strategies for developing rotavirus (RV) vaccines have always been controversial. At present, both the monovalent RV vaccine and the multivalent RV vaccine have displayed excellent safety and efficacy against RV infection and shown cross-reactive immunity, which laid the question whether the multivalent RV vaccine could be replaced by the monovalent RV vaccine. In this study, we focused on comparing the immunogenicity (serum neutralization activity and protection against homotypic and heterotypic RVs’ challenge) of individual standard RV strains (monovalent RV immunogens) and different combinations of them (multivalent RV immunogens). In result, RV immunogens showed general immunogenicity and heterotypic reaction but the multivalent RV immunogens exhibited greater serum neutralization activity and stronger heterotypic reaction than the monovalent RV immunogens (P<0.05). As to the protection, the multivalent RV immunogens also revealed more rapid and stronger protection against homotypic and heterotypic RVs’ challenge than the monovalent RV immunogens. The results demonstrated that both the monovalent and multivalent RV immunogens exhibited high immunogenicity, but the monovalent RV immunogens could not provide enough neutralization antibodies to protect MA104 cells against the infection with heterotypic RV strains and timely protection against homotypic and heterotypic RVs, so the multivalent RV vaccine could not be replaced by the monovalent RV vaccine.

A paradox of transcriptional and functional innate interferon responses of human intestinal enteroids to enteric virus infection

The intestinal epithelium can limit enteric pathogens by producing antiviral cytokines, such as IFNs. Type I IFN (IFN-α/β) and type III IFN (IFN-λ) function at the epithelial level, and their respective efficacies depend on the specific pathogen and site of infection. However, the roles of type I and type III IFN in restricting human enteric viruses are poorly characterized as a result of the difficulties in cultivating these viruses in vitro and directly obtaining control and infected small intestinal human tissue. We infected nontransformed human intestinal enteroid cultures from multiple individuals with human rotavirus (HRV) and assessed the host epithelial response by using RNA-sequencing and functional assays. The dominant transcriptional pathway induced by HRV infection is a type III IFN-regulated response. Early after HRV infection, low levels of type III IFN protein activate IFN-stimulated genes. However, this endogenous response does not restrict HRV replication because replication-competent HRV antagonizes the type III IFN response at pre- and posttranscriptional levels. In contrast, exogenous IFN treatment restricts HRV replication, with type I IFN being more potent than type III IFN, suggesting that extraepithelial sources of type I IFN may be the critical IFN for limiting enteric virus replication in the human intestine.

Epidemiology of group A rotavirus infection after the introduction of monovalent vaccine in the National Immunization Program of Saudi Arabia

This study aimed to investigate the prevalence of group A rotavirus (RVA) gastroenteritis and the distribution of the RVA genotypes as well as to determine a possible change in the age of occurrence of the RVA infection in the first 2 years after Rotarix® vaccine introduction in Saudi Arabia. This descriptive study included 850 hospitalized children <5 years of age with acute gastroenteritis (AG) between October 2013 and September 2015. Overall, 78 (9.2%) children were positive for RVA during the study period with a positivity rate ranging from 11.3% in the first year of the study to 6.8% in the second year. G1 (47.4%) was the predominant G type, followed by G2 (28.2%) and G9 (10.3%). The most common P type was P[8] (69.2%) followed by P[4] (25.6%). The decrease in the prevalence of G1P[8] from 51% to 37.1% was associated with an increase in the prevalence of G2P[4] from 21.6% to 33.3% during the 2-year study period. This study demonstrated a significant decrease in the prevalence of RVA-AG cases in the first 2-year period after vaccine introduction, especially in the age group between 1 and 12 months, and a reduction in the circulation of G1P[6]. The parallel rise and spread of G2P[4] in post-vaccination period might pose an impact to long-term vaccine efficacy. Continued surveillance studies in different Saudi regions are crucial to document the effectiveness of Rotarix® vaccine and evaluate the potential emergence of rare/novel RVA genotypes. J. Med. Virol. 89:429-434, 2017. © 2016 Wiley Periodicals, Inc.

In-season and out-of-season variation of rotavirus genotype distribution and age of infection across 12 European countries before the introduction of routine vaccination, 2007/08 to 2012/13

The EuroRotaNet surveillance network has conducted rotavirus genotype surveillance since 2007 in 16 European countries. Using epidemiological and microbiological data from 39,786 genotyped rotavirus-positive specimens collected between September 2007 and August 2013, we assessed genotype distribution and age distribution of rotavirus gastroenteritis (RVGE) cases in and out of peak season in 12 countries which were yet to implement routine rotavirus vaccination. In multinomial multivariate logistic regression, adjusting for year, country and age, the odds of infection caused by genotype-constellation 2 DS-1-like stains (adjusted multinomial odds ratio (aM-OR) = 1.25; 95% confidence interval (CI): 1.13-1.37; p < 0.001), mixed or untypable genotypes (aM-OR = 1.55; 95% CI: 1.40-1.72; p < 0.001) and less common genotypes (aM-OR = 2.11; 95% CI:1.78-2.51; p < 0.001) increased out of season relative to G1P[8]. Age varied significantly between seasons; the proportion of RVGE cases younger than 12 months in the United Kingdom increased from 34% in season to 39% out of season (aM-OR = 1.66; 95% CI: 1.20-2.30), and the proportion five years and older increased from 9% in season to 17% out of season (aM-OR = 2.53; 95% CI: 1.67-3.82). This study provides further understanding of the rotavirus ecology before vaccine introduction, which will help interpret epidemiological changes in countries introducing or expanding rotavirus vaccination programmes.

Population Impact and Effectiveness of Monovalent Rotavirus Vaccination in Urban Malawian Children 3 Years After Vaccine Introduction: Ecological and Case-Control Analyses

BACKGROUND

Rotavirus vaccines have been introduced in many low-income African countries including Malawi in 2012. Despite early evidence of vaccine impact, determining persistence of protection beyond infancy, the utility of the vaccine against specific rotavirus genotypes, and effectiveness in vulnerable subgroups is important.

METHODS

We compared rotavirus prevalence in diarrheal stool and hospitalization incidence before and following rotavirus vaccine introduction in Malawi. Using case-control analysis, we derived vaccine effectiveness (VE) in the second year of life and for human immunodeficiency virus (HIV)-exposed and stunted children.

RESULTS

Rotavirus prevalence declined concurrent with increasing vaccine coverage, and in 2015 was 24% compared with prevaccine mean baseline in 1997-2011 of 32%. Since vaccine introduction, population rotavirus hospitalization incidence declined in infants by 54.2% (95% confidence interval [CI], 32.8-68.8), but did not fall in older children. Comparing 241 rotavirus cases with 692 test-negative controls, VE was 70.6% (95% CI, 33.6%-87.0%) and 31.7% (95% CI, -140.6% to 80.6%) in the first and second year of life, respectively, whereas mean age of rotavirus cases increased from 9.3 to 11.8 months. Despite higher VE against G1P[8] than against other genotypes, no resurgence of nonvaccine genotypes has occurred. VE did not differ significantly by nutritional status (78.1% [95% CI, 5.6%-94.9%] in 257 well-nourished and 27.8% [95% CI, -99.5% to 73.9%] in 205 stunted children;P= .12), or by HIV exposure (60.5% [95% CI, 13.3%-82.0%] in 745 HIV-unexposed and 42.2% [95% CI, -106.9% to 83.8%] in 174 exposed children;P= .91).

CONCLUSIONS

Rotavirus vaccination in Malawi has resulted in reductions in disease burden in infants <12 months, but not in older children. Despite differences in genotype-specific VE, no genotype has emerged to suggest vaccine escape. VE was not demonstrably affected by HIV exposure or stunting.

Molecular characterisation of wild-type G1P[8] and G3P[8] rotaviruses isolated in Vietnam 2008 during a vaccine trial

Rotavirus vaccines work better in developed countries than in developing countries, leading to the question of whether the circulating strains are different in these two settings. In 2008, a clinical trial of the pentavalent rotavirus vaccine was performed in Nha Trang, Vietnam, in which the efficacy was reported to be 64 %. Although samples were collected independently from the clinical trial, we examined faecal specimens from children hospitalised for rotavirus diarrhoea and found that G3P[8] and G1P[8] were co-dominant at the time of the clinical trial. The aim of this study was to explore whether they were divergent from the strains circulating in the developed countries where the vaccine efficacy is high. Two G3P[8] and two G1P[8] strains that were regarded as representatives based on their electropherotypes were selected for full-genome sequencing. The genotype constellation was G1/G3-P[8]-I1-R1-C1-M1-A1-N1-T1-E1-H1. All but the VP4 genes, one of which belonged to the emerging P[8]b genotype (OP354-like VP4), clustered into one or more lineages/alleles with the strains circulating in developed countries, with ≥97.5 % nucleotide sequence identity. Additionally, 10 G1 and 12 G3 VP7 sequences as well as 31 VP4 sequences were determined. No amino acid differences were observed between the Vietnamese strains and strains in the developed countries that were likely to have affected the neutralisation specificity of their VP7 and VP4. In conclusion, apart from prevalent P[8]b VP4, virtually no differences were observed between the predominant strains circulating in Vietnam at the time of the clinical trial and the strains in the developed countries; hence, the lower vaccine efficacy was more likely to be due to factors other than strain divergence.

Did Large-Scale Vaccination Drive Changes in the Circulating Rotavirus Population in Belgium?

Vaccination can place selective pressures on viral populations, leading to changes in the distribution of strains as viruses evolve to escape immunity from the vaccine. Vaccine-driven strain replacement is a major concern after nationwide rotavirus vaccine introductions. However, the distribution of the predominant rotavirus genotypes varies from year to year in the absence of vaccination, making it difficult to determine what changes can be attributed to the vaccines. To gain insight in the underlying dynamics driving changes in the rotavirus population, we fitted a hierarchy of mathematical models to national and local genotype-specific hospitalization data from Belgium, where large-scale vaccination was introduced in 2006. We estimated that natural- and vaccine-derived immunity was strongest against completely homotypic strains and weakest against fully heterotypic strains, with an intermediate immunity amongst partially heterotypic strains. The predominance of G2P[4] infections in Belgium after vaccine introduction can be explained by a combination of natural genotype fluctuations and weaker natural and vaccine-induced immunity against infection with strains heterotypic to the vaccine, in the absence of significant variation in strain-specific vaccine effectiveness against disease. However, the incidence of rotavirus gastroenteritis is predicted to remain low despite vaccine-driven changes in the distribution of genotypes.

Qualitative Effects of Monovalent Vaccination Against Rotavirus: A Comparison of North America and South America

Rotavirus is the most common cause of severe gastroenteritis in young children worldwide. The introduction of vaccination programs has led to a significant reduction in number of hospitalizations due to rotavirus in North and South American countries. Little work has been done, however, to examine the differential impact of vaccination as a function of strain distribution and strain-specific vaccine efficacy. We developed a two-strain epidemiological model of rotavirus transmission, and used it to examine the effects of a monovalent vaccine (Rotarix) on the qualitative behaviors of infection levels in a population. For contrast, we parameterized our model with strain distribution data from North America and from South America. In all cases, the introduction of the vaccine led to significant decreases in the prevalence of primary infection due to both strains for a decade or more, after which the overall prevalence recovers to near pre-vaccination levels. The prevalence of G1P[8] is significantly higher in North America (73 % of all rotavirus infections) compared to that in South America (34 %). Our model predicts that the introduction of Rotarix might result in major strain replacement in regions such as North America where the prevalence of G1P[8] is relatively high, due to higher efficacy of Rotarix against infection caused by G1P[8], while regions with lower prevalence of G1P[8], such as South America, are not susceptible to major strain replacement.