Evaluation of the efficacy of a low-passage bovine rotavirus (strain WC3) vaccine in children in Central Africa

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

IMPORTANCE

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

OBJECTIVE

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

DATA SOURCES

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

STUDY SELECTION

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

DATA EXTRACTION AND SYNTHESIS

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

MAIN OUTCOMES AND MEASURES

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

RESULTS

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

CONCLUSIONS AND RELEVANCE

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

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

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

The multifaceted roles of breast milk antibodies

Neonates are born with an immature immune system and rely on the transfer of immunity from their mothers. Maternal antibodies are transferred via the placenta and breast milk. Although the role of placentally transferred immunoglobulin G (IgG) is established, less is known about the selection of antibodies transferred via breast milk and the mechanisms by which they provide protection against neonatal disease. Evidence suggests that breast milk antibodies play multifaceted roles, preventing infection and supporting the selection of commensals and tolerizing immunity during infancy. Here, we discuss emerging data related to the importance of breast milk antibodies in neonatal immunity and development.

Reviewing the evidence on breast milk composition and immunological outcomes

A large number of biologically active components have been found in human milk (HM), and in both human and animal models, studies have provided some evidence suggesting that HM composition can be altered by maternal exposures, subsequently influencing health outcomes for the breastfed child. Evidence varies from the research studies on whether breastfeeding protects the offspring from noncommunicable diseases, including those associated with immunological dysfunction. It has been hypothesized that the conflicting evidence results from HM composition variations, which contain many immune active molecules, oligosaccharides, lactoferrin, and lysozyme in differing concentrations, along with a diverse microbiome. Determining the components that influence infant health outcomes in terms of both short- and long-term sequelae is complicated by a lack of understanding of the environmental factors that modify HM constituents and thereby offspring outcomes. Variations in HM immune and microbial composition (and the differing infantile responses) may in part explain the controversies that are evidenced in studies that aim to evaluate the prevalence of allergy by prolonged and exclusive breastfeeding. HM is a "mixture" of immune active factors, oligosaccharides, and microbes, which all may influence early immunological outcomes. This comprehensive review provides an in-depth overview of existing evidence on the studied relationships between maternal exposures, HM composition, vaccine responses, and immunological outcomes.

Challenges to Developing a Rotavirus Vaccine

Rotavirus is the most important cause of gastroenteritis worldwide. In developing countries, the virus is a major cause of death in infants and young children. In the United States, before the licensure of vaccines, rotavirus infections accounted for ∼2.7 million cases of gastroenteritis annually. Here are described the history and challenges surrounding the development of a rotavirus vaccine.

Effect of pentavalent rotavirus vaccine introduction on hospital admissions for diarrhoea and rotavirus in children in Rwanda: a time-series analysis

BACKGROUND

In May, 2012, Rwanda became the first low-income African country to introduce pentavalent rotavirus vaccine into its routine national immunisation programme. Although the potential health benefits of rotavirus vaccination are huge in low-income African countries that account for more than half the global deaths from rotavirus, concerns remain about the performance of oral rotavirus vaccines in these challenging settings.

METHODS

We conducted a time-series analysis to examine trends in admissions to hospital for non-bloody diarrhoea in children younger than 5 years in Rwanda between Jan 1, 2009, and Dec 31, 2014, using monthly discharge data from the Health Management Information System. Additionally, we reviewed the registries in the paediatric wards at six hospitals from 2009 to 2014 and abstracted the number of total admissions and admissions for diarrhoea in children younger than 5 years by admission month and age group. We studied trends in admissions specific to rotavirus at one hospital that had undertaken active rotavirus surveillance from 2011 to 2014. We assessed changes in rotavirus epidemiology by use of data from eight active surveillance hospitals.

FINDINGS

Compared with the 2009-11 prevaccine baseline, hospital admissions for non-bloody diarrhoea captured by the Health Management Information System fell by 17-29% from a pre-vaccine median of 4051 to 2881 in 2013 and 3371 in 2014, admissions for acute gastroenteritis captured in paediatric ward registries decreased by 48-49%, and admissions specific to rotavirus captured by active surveillance fell by 61-70%. The greatest effect was recorded in children age-eligible to be vaccinated, but we noted a decrease in the proportion of children with diarrhoea testing positive for rotavirus in almost every age group.

INTERPRETATION

The number of admissions to hospital for diarrhoea and rotavirus in Rwanda fell substantially after rotavirus vaccine implementation, including among older children age-ineligible for vaccination, suggesting indirect protection through reduced transmission of rotavirus. These data highlight the benefits of routine vaccination against rotavirus in low-income settings.

FUNDING

Gavi, the Vaccine Alliance and the Government of Rwanda.

Insights from global data for use of rotavirus vaccines in India

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

Rotavirus vaccines in routine use

Vaccines are now available to combat rotavirus, the most common cause of severe diarrhea among children worldwide. We review clinical trial data for available rotavirus vaccines and summarize postlicensure data on effectiveness, impact, and safety from countries routinely using these vaccines in national programs. In these countries, rotavirus vaccines have reduced all-cause diarrhea and rotavirus hospitalizations by 17%-55% and 49%-92%, respectively, and all-cause diarrhea deaths by 22%-50% in some settings. Indirect protection of children who are age-ineligible for rotavirus vaccine has also been observed in some high and upper middle income countries. Experience with routine use of rotavirus vaccines in lower middle income countries has been limited to date, but vaccine introductions in such countries have been increasing in recent years. The risk-benefit analysis of rotavirus vaccines is extremely favorable but other strategies to improve the effectiveness of the vaccine, particularly in lower middle income settings, should be considered.

Remaining issues and challenges for rotavirus vaccine in preventing global childhood diarrheal morbidity and mortality

Rotavirus vaccines have had a dramatic impact on morbidity and mortality from diarrhea among children in high- and middle-income countries that have introduced the vaccine into their national immunization programs. Widespread introduction of rotavirus vaccine in developing countries is imminent and their full potential in reducing the global burden from severe childhood diarrhea may soon be realized. The objectives of this paper are to describe the remaining issues and challenges in ensuring the success of the global rotavirus vaccination program and to discuss further research needed to help address them.

Why does the world need another rotavirus vaccine?

A “Meeting on Upstream Rotavirus Vaccines and Emerging Vaccine Producers” was held at the World Health Organization in Geneva, Switzerland on March 28–30, 2006. The purpose was to discuss, evaluate, and weigh the importance of additional rotavirus vaccine candidates following the successful international licensure of rotavirus vaccines by two major pharmaceutical companies (GlaxoSmithKline and Merck) that had been in development for many years. Both licensed vaccines are composed of live rotaviruses that are delivered orally as have been all candidate rotavirus vaccines evaluated in humans. Each is built on the experience gained with previous candidates whose development had either been discontinued or, in the case of the previously licensed rhesus rotavirus reassortant vaccine (Rotashield), was withdrawn by its manufacturer after the discovery of a rare association with intussusception. Although which alternative candidate vaccines should be supported for development and where this should be done are controversial topics, there was general agreement expressed at the Geneva meeting that further development of alternative candidates is a high priority. This development will help insure that the most safe, effective and economic vaccines are available to children in Third World nations where the vast majority of the >600,000 deaths due to rotavirus occur each year. This review is intended to provide the history and present status of rotavirus vaccines as well as a perspective on the future development of candidate vaccines as a means of promulgating plans suggested at the Geneva meeting.

Performance of rotavirus vaccines in developed and developing countries

The World Health Organization estimates that rotavirus diarrhea results in approximately half a million deaths and approximately 2.4 million hospitalizations in developing countries each year. Two live oral rotavirus vaccines, RotaTeq® (RV 5; Merck) and Rotarix® (RV 1; GlaxoSmithKline) with good efficacy against severe rotavirus disease and a reassuring safety profile could substantially impact the burden of rotavirus disease. In April 2009, WHO provided a recommendation for global introduction of these vaccines in national immunization programs of developing countries worldwide. In this article, we review published data on previous candidate rotavirus vaccines and vaccines in current use, with emphasis on their performance in developed versus developing countries. In developed countries, both first and second generation rotavirus vaccines have demonstrated high efficacy against severe rotavirus disease (pooled efficacy = 73% and 85%, respectively). In developing countries, small early trials for the first generation vaccines failed to provide protection against rotavirus disease (pooled efficacy = 20%), however, trials of the second generation vaccines yielded substantial improvements in efficacy in developing countries (pooled efficacy of 51%), leading to a global recommendation for rotavirus vaccine introduction by WHO. Future efforts for these vaccines should focus on optimizing the efficacy and delivery of these vaccines in challenging target populations of Asia and Africa with the greatest burden of severe rotavirus disease.

Rotavirus infection: a perspective on epidemiology, genomic diversity and vaccine strategies

For centuries, acute diarrhea has been a major cause of death in young children worldwide, and until 1973, before rotavirus was discovered; no infectious agents could be identified in about 80% of patients admitted to hospital with severe dehydrating diarrhea. Rotaviruses have now been shown to cause 40-50% of severe acute diarrhea in young children worldwide in both developing and developed countries. More than 600,000 young children die and approximately 2.4 million hospitalize annually from rotavirus disease, especially in South-East Asia and sub-Saharan Africa. Two safe and effective vaccines are now licensed in 100 countries but used in 17 countries. Rotarix (GSK) vaccine is derived from single attenuated human rotavirus G1P[8], representative of the most common serotype identified worldwide. RotaTeq (Merck) is a pentavalent mixture of naturally attenuated bovine/human rotavirus reassortants representing G1, G2, G3, G4, and P[8] serotypes. Though these vaccines have already dramatically decreased the morbidity associated with rotavirus in countries where they are widely used, the third generation of vaccines, based on inactivated viruses or recombinant virus like particle are already in pipeline. Continuous surveillance and the genetic and antigenic analysis of the various strains of rotavirus circulating worldwide will aid significantly in assessing the effectiveness of these vaccines and monitor emergence of new strains. Introduction of rotavirus vaccines in national vaccine policy along with other childhood vaccines may result in significant reduction in mortality in children in poor socioeconomic countries.

Uniformity of rotavirus strain nomenclature proposed by the Rotavirus Classification Working Group (RCWG)

In April 2008, a nucleotide-sequence-based, complete genome classification system was developed for group A rotaviruses (RVs). This system assigns a specific genotype to each of the 11 genome segments of a particular RV strain according to established nucleotide percent cutoff values. Using this approach, the genome of individual RV strains are given the complete descriptor of Gx-P[x]-Ix-Rx-Cx-Mx-Ax-Nx-Tx-Ex-Hx. The Rotavirus Classification Working Group (RCWG) was formed by scientists in the field to maintain, evaluate and develop the RV genotype classification system, in particular to aid in the designation of new genotypes. Since its conception, the group has ratified 51 new genotypes: as of April 2011, new genotypes for VP7 (G20-G27), VP4 (P[28]-P[35]), VP6 (I12-I16), VP1 (R5-R9), VP2 (C6-C9), VP3 (M7-M8), NSP1 (A15-A16), NSP2 (N6-N9), NSP3 (T8-T12), NSP4 (E12-E14) and NSP5/6 (H7-H11) have been defined for RV strains recovered from humans, cows, pigs, horses, mice, South American camelids (guanaco), chickens, turkeys, pheasants, bats and a sugar glider. With increasing numbers of complete RV genome sequences becoming available, a standardized RV strain nomenclature system is needed, and the RCWG proposes that individual RV strains are named as follows: RV group/species of origin/country of identification/common name/year of identification/G- and P-type. In collaboration with the National Center for Biotechnology Information (NCBI), the RCWG is also working on developing a RV-specific resource for the deposition of nucleotide sequences. This resource will provide useful information regarding RV strains, including, but not limited to, the individual gene genotypes and epidemiological and clinical information. Together, the proposed nomenclature system and the NCBI RV resource will offer highly useful tools for investigators to search for, retrieve, and analyze the ever-growing volume of RV genomic data.

Global impact of rotavirus vaccines

The WHO has recently recommended the inclusion of rotavirus vaccine in the national immunization programs of all countries. In countries in the Americas, Europe and Australia that have adopted routine childhood immunization against rotavirus, significant reductions in the burden of severe childhood diarrhea have been observed. Besides protecting vaccinated children, disease rates also appear to be reduced in unvaccinated children, suggesting indirect benefits from vaccination (i.e., herd protection). Early clinical trial data from Africa and Asia are promising, and further efforts are needed to optimize the benefits of vaccination in developing countries where vaccines are likely to have their greatest impact.

Development of a rotavirus vaccine: clinical safety, immunogenicity, and efficacy of the pentavalent rotavirus vaccine, RotaTeq

Initial approaches for rotavirus vaccines were based on the classical "Jennerian" approach and utilized simian and bovine rotavirus strains, which provided cross-protection against human rotavirus strains but did not cause illness in infants and young children because of their species-specific tropism. The demonstrated efficacy of these vaccines was not consistent across studies. Thus, human-animal reassortants containing an animal rotavirus backbone with human rotavirus surface G and/or P proteins were developed, which demonstrated more consistent efficacy than that observed with the non-reassortant rotavirus strains. The pentavalent rotavirus vaccine, RotaTeq, contains 5 human-bovine reassortant rotaviruses consisting of a bovine (WC3) backbone with human rotavirus surface proteins representative of the most common G (G1, G2, G3, G4) or P (P1A[8]) types worldwide. The present review focuses on the development of the pentavalent rotavirus vaccine RotaTeq. Results of a large-scale Phase III clinical study showed that three doses of RotaTeq were immunogenic, efficacious, and well tolerated with no increased clinical risk of intussusception. RotaTeq was efficacious against rotavirus gastroenteritis of any severity (74%) and severe disease (98-100%), using a validated clinical scoring system. Reductions in rotavirus-associated hospitalizations and emergency department (ED) visits, for up to 2 years post-vaccination, were 95% in Europe, 97% in the United States, and 90% in the Latin American/Caribbean regions. RotaTeq was recently shown to be up to 100% effective in routine use in the US in reducing hospitalizations and ED visits and 96% effective in reducing physician visits. Additional studies in 8 different locations in the US have shown 85-95% reduction in rotavirus-associated hospitalizations and/or ED visits in the first 2-2.5 years of routine use.

Effect of human rotavirus vaccine on severe diarrhea in African infants

BACKGROUND

Rotavirus is the most common cause of severe gastroenteritis among young children worldwide. Data are needed to assess the efficacy of the rotavirus vaccine in African children.

METHODS

We conducted a randomized, placebo-controlled, multicenter trial in South Africa (3166 infants; 64.1% of the total) and Malawi (1773 infants; 35.9% of the total) to evaluate the efficacy of a live, oral rotavirus vaccine in preventing severe rotavirus gastroenteritis. Healthy infants were randomly assigned in a 1:1:1 ratio to receive two doses of vaccine (in addition to one dose of placebo) or three doses of vaccine--the pooled vaccine group--or three doses of placebo at 6, 10, and 14 weeks of age. Episodes of gastroenteritis caused by wild-type rotavirus during the first year of life were assessed through active follow-up surveillance and were graded with the use of the Vesikari scale.

RESULTS

A total of 4939 infants were enrolled and randomly assigned to one of the three groups; 1647 infants received two doses of the vaccine, 1651 infants received three doses of the vaccine, and 1641 received placebo. Of the 4417 infants included in the per-protocol efficacy analysis, severe rotavirus gastroenteritis occurred in 4.9% of the infants in the placebo group and in 1.9% of those in the pooled vaccine group (vaccine efficacy, 61.2%; 95% confidence interval, 44.0 to 73.2). Vaccine efficacy was lower in Malawi than in South Africa (49.4% vs. 76.9%); however, the number of episodes of severe rotavirus gastroenteritis that were prevented was greater in Malawi than in South Africa (6.7 vs. 4.2 cases prevented per 100 infants vaccinated per year). Efficacy against all-cause severe gastroenteritis was 30.2%. At least one serious adverse event was reported in 9.7% of the infants in the pooled vaccine group and in 11.5% of the infants in the placebo group.

CONCLUSIONS

Human rotavirus vaccine significantly reduced the incidence of severe rotavirus gastroenteritis among African infants during the first year of life. (ClinicalTrials.gov number, NCT00241644.)

Oral rotavirus vaccines: how well will they work where they are needed most?

Rotavirus vaccines hold promise to decrease the burden of severe diarrhea in the poorest countries, where 85% of deaths due to rotavirus occur. However, the potency of live oral vaccines is lower in these challenging settings than in middle- and upper-income countries. Many hypotheses have been suggested to explain these differences that could provide clues to improve the ultimate success of these novel vaccines. Although introduction today of even moderately effective vaccines will decrease the morbidity and mortality associated with rotavirus in low-income settings, research is urgently needed to understand why these differences in efficacy occur and what could be done to improve vaccine performance to maximize the life-saving benefits of vaccination.

Public health impact and cost effectiveness of mass vaccination with live attenuated human rotavirus vaccine (RIX4414) in India: model based analysis

OBJECTIVES

To examine the public health impact of mass vaccination with live attenuated human rotavirus vaccine (RIX4414) in a birth cohort in India, and to estimate the cost effectiveness and affordability of such a programme.

DESIGN

Decision analytical Markov model encompassing all direct medical costs. Infection risk and severity depended on age, number of previous infections, and vaccination history; probabilities of use of inpatient and outpatient health services depended on symptom severity.

DATA SOURCES

Published clinical, epidemiological, and economic data. When possible, parameter estimates were based on data specific for India. Population Simulated Indian birth cohort followed for five years.

MAIN OUTCOME MEASURES

Decrease in rotavirus gastroenteritis episodes (non-severe and severe), deaths, outpatient visits, and admission to hospital; incremental cost effectiveness ratio of vaccination expressed as net cost in 2007 rupees per life year saved.

RESULTS

In the base case, vaccination prevented 28,943 (29.7%) symptomatic episodes, 6981 (38.2%) severe episodes, 164 deaths (41.0%), 7178 (33.3%) outpatient visits, and 812 (34.3%) admissions to hospital per 100,000 children. Vaccination cost 8023 rupees (about pound100, euro113, $165) per life year saved, less than India's per capita gross domestic product, a common criterion for cost effectiveness. The net programme cost would be equivalent to 11.6% of the 2006-7 budget of the Indian Department of Health and Family Welfare. Model results were most sensitive to variations in access to outpatient care for those with severe symptoms. If this parameter was increased to its upper limit, the incremental cost effectiveness ratio for vaccination still fell between one and three times the per capita gross domestic product, meeting the World Health Organization's criterion for "cost effective" interventions. Uncertainty analysis indicated a 94.7% probability that vaccination would be cost effective according to a criterion of one times per capita gross domestic product per life year saved, and a 97.8% probability that it would be cost effective according to a criterion of three times per capita gross domestic product.

CONCLUSIONS

Across a wide range of assumptions, mass RIX4414 vaccination in India would probably prevent substantial morbidity and mortality at a cost per life year saved below typical thresholds of cost effectiveness. The opportunity costs of such a programme in this or similar settings, however, should be weighed up carefully.

Implementing rotavirus vaccination in Asia

At the 2006 meeting of the Asian Pacific Pediatric Association (APPA), the Asia Pacific regional rotavirus community and international experts strongly recommended that rotavirus vaccines be used in National Immunization Programmes (NIP) in countries in Asia. Two rotavirus vaccine candidates are currently licensed and have been demonstrated to be safe, well tolerated and highly efficacious. Several additional vaccines are in the late stages of development. The conference participants agreed that decisions on the introduction of rotavirus vaccines may require additional disease burden data in some countries and that economic evaluations will help policymakers reach decisions on nationwide rotavirus vaccine implementation. Other potential issues that arise with vaccine implementation, for example, the concomitant use of rotavirus vaccines with other vaccines, were also discussed. Rotavirus vaccines have the potential to substantially reduce morbidity and mortality from rotavirus disease and impact children's health in Asia.

Rotavirus vaccines: recent developments and future considerations

Two new vaccines have recently been shown to be safe and effective in protecting young children against severe rotavirus gastroenteritis. Although both vaccines are now marketed worldwide, it is likely that improvements to these vaccines and/or the development of future generations of rotavirus vaccines will be desirable. This Review addresses recent advances in our knowledge of rotavirus, the host immune response to rotavirus infection and the efficacy and safety of the new vaccines that will be helpful for improving the existing rotavirus vaccines, or developing new rotavirus vaccines in the future.

Identification of an immunodominant CD4+ T cell epitope in the VP6 protein of rotavirus following intranasal immunization of BALB/c mice

The only lymphocytes required for protection against fecal rotavirus shedding after intranasal immunization of BALB/c (H-2(d)) mice with a chimeric rotavirus VP6 protein (MBPColon, two colonsVP6) and the mucosal adjuvant LT(R192G) are CD4(+) T cells. The purpose of this study was to identify CD4(+) T cell epitopes within VP6 that might be responsible for this protection. To make this determination, spleen cells obtained from BALB/c mice following intranasal immunization with MBPColon, two colonsVP6/LT(R192G) were stimulated in vitro with either MBPColon, two colonsVP6 or overlapping VP6 peptides containing <or=30 amino acids (AA). The numbers of memory (CD44(high)) CD4(+) T cells stimulated to produce T(H)1 and T(H)17 cytokines (IFNgamma and IL-17), as well as the quantities of these cytokines released into the cell supernatants, were then measured relative to those produced in mock-stimulated cells from the same animals. One epitope expected to be found was the VP6 14-mer AA(289-302), previously identified as a CD4(+) T cell epitope in H-2(d) mice. This was not observed but instead the only VP6 epitope identified was AA(242-259), the dominant CD4(+) T cell epitope previously reported after oral, live rotavirus immunization.

Intrarectal immunization of mice with VP6 and either LT(R192G) or CTA1-DD as adjuvant protects against fecal rotavirus shedding after EDIM challenge

Intranasal or oral delivery of the chimeric rotavirus VP6 protein MBP::VP6 to mice elicited >90% reductions in fecal rotavirus shedding after murine rotavirus challenge. Protection depended on co-administration of adjuvants, the most effective being bacterial toxins. Because of safety and efficacy concerns following intranasal or oral toxin delivery, protective efficacy of MBP::VP6 after intrarectal delivery with toxin adjuvants was determined and compared to that induced after intranasal and oral immunization. Adult BALB/c mice were orally challenged with the murine rotavirus strain EDIM 4 weeks after their second immunization with MBP::VP6 and either LT(R192G), an attenuated Escherichia coli heat-labile toxin, or CTA1-DD, a cholera toxin derivative. Reductions in fecal rotavirus shedding were then determined relative to mock-immunized mice. Immunization with MBP::VP6 and either adjuvant by any route (except oral immunization with CTA1-DD) significantly (P<0.0001) reduced rotavirus shedding. As was previously found after oral and intranasal immunization, intrarectal immunization with MBP::VP6 and adjuvant was associated with T cell responses (IFNgamma and IL-17) but not B cell (antibody) responses.

Rotavirus vaccines: current prospects and future challenges

Rotavirus is the most common cause of severe diarrhoea in children worldwide and diarrhoeal deaths in children in developing countries. Accelerated development and introduction of rotavirus vaccines into global immunisation programmes has been a high priority for many international agencies, including WHO and the Global Alliance for Vaccines and Immunizations. Vaccines have been developed that could prevent the enormous morbidity and mortality from rotavirus and their effect should be measurable within 2-3 years. Two live oral rotavirus vaccines have been licensed in many countries; one is derived from an attenuated human strain of rotavirus and the other combines five bovine-human reassortant strains. Each vaccine has proven highly effective in preventing severe rotavirus diarrhoea in children and safe from the possible complication of intussusception. In developed countries, these vaccines could substantially reduce the number and associated costs of child hospitalisations and clinical visits for acute diarrhoea. In developing countries, they could reduce deaths from diarrhoea and improve child survival through programmes for childhood immunisations and diarrhoeal disease control. Although many scientific, programmatic, and financial challenges face the global use of rotavirus vaccines, these vaccines-and new candidates in the pipeline-hold promise to make an immediate and measurable effect to improve child health and survival from this common burden affecting all children.

The new pentavalent rotavirus vaccine composed of bovine (strain WC3) -human rotavirus reassortants

BACKGROUND

Infantile gastroenteritis caused by human rotaviruses is a prevalent disease throughout the world, causing dehydration and hospitalization in all countries. In developing countries, it is associated with a high mortality. A licensed vaccine against rotavirus was withdrawn because of a causal association with intussusception. A new vaccine has been developed and is a candidate for licensure.

METHODS

To recount the early development and recent demonstration of the safety and efficacy of the new vaccine. A bovine rotavirus attenuated for humans was isolated and reassorted with human rotaviruses of serotypes G1-4 and P1 to create a pentavalent vaccine. Multiple placebo-controlled clinical trials, including one involving approximately 70,000 infants, were conducted in multiple developed countries.

RESULTS

The pentavalent vaccine was well tolerated by infants less than 8 months of age, and the incidence of intussusception was similar among vaccine and placebo recipients. More than 90% of infants had a significant rise in serum antirotavirus IgA titer after 3 doses. Efficacy of 95% against severe disease causing hospitalization or emergency care was demonstrated, and pentavalent vaccine prevented 74% of all rotavirus disease.

CONCLUSIONS

If widely used, pentavalent vaccine would control rotavirus disease in the United States and other developed countries and could also have a major effect in developing countries.

Rotavirus vaccine: early introduction in Latin America-risks and benefits

Rotavirus infection is the cause of severe gastroenteritis of young children worldwide, leading to an estimate of 600,000 deaths a year. Efforts to develop an effective and safe vaccine resulted in licensing in 1998 of a live oral vaccine (RotaShield) that was withdrawn less than 1 year later when reports of cases of intussusception were linked to its application. This led to development of new rotavirus vaccine candidates that are currently in late phase III clinical trials. One of these vaccines, GlaxoSmithKline's Rotarix, was licensed in July 2004 to be used in Mexico. This review describes the general background for rotavirus vaccine development, the different vaccine candidates that have been tested or are currently being evaluated, the association of rotavirus vaccination with the bowel blockage known as intussuception, and discusses the benefits and risks of the fast-track introduction of Rotarix in Latin America, and particularly in Mexico.

A Rotavirus Vaccine for Infants: The Asian Experience

Introduction: Severe rotavirus gastroenteritis in children causes significant morbidity world- wide and substantial deaths in developing countries. Hence, a live attenuated vaccine Rotarix™ was developed with human strain RIX4414 of G1P1A P[8] specificity. RIX4414 trials in infants have begun in developed and developing countries worldwide. An overview of RIX4414 in developed and developing countries and prospects with this vaccine in Asia are presented. Methods: Completed RIX4414 trials have been reviewed. Results: Two oral doses of RIX4414 were well tolerated with a reactogenicity profile similar to placebo. RIX4414 was also highly immunogenic, e.g., in a dose-ranging study conducted in Singapore, 98.8% to100% of infants had a vaccine take after 2 doses. RIX4414 did not affect the immune response of simultaneously administered routine infant vaccines. RIX4414 significantly reduced severe rotavirus gastroen- teritis in settings where multiple serotypes including the emerging G9 type co-circulated. Conclusion: These encouraging results warrant further evaluation of the vaccine worldwide and especially in developing countries with the highest need. Therefore, evaluation of the Rotarix™ vaccine is continuing in large phase III trials in Asia and worldwide. Key words: Asia, Attenuated, Developing countries, Gastroenteritis, RIX4414

Clinical trials of rotavirus vaccines in Europe

Clinical trials of a live oral candidate rotavirus vaccine were started in 1982 and soon demonstrated that severe rotavirus disease can be prevented by vaccination. The first bovine candidate vaccine was withdrawn because of inconsistent efficacy, and studies of a rhesus rotavirus vaccine were initiated. A field trial of rhesus-human reassortant tetravalent rotavirus vaccine in Finland was pivotal for the licensure of this vaccine (RotaShield) in the United States in 1998. However, this vaccine was withdrawn in 1999 because of association with intussusception. Safety therefore became a major issue in the development of new candidate rotavirus vaccines. A pentavalent bovine-human reassortant rotavirus vaccine (RotaTeq) showed about 70% efficacy against any rotavirus disease and 100% efficacy against severe disease in Finland, according to the Clark scale. A large, multinational safety trial indicated no association of this vaccine with intussusception, and its licensure is under review in the EU. An attenuated human rotavirus vaccine (RIX4414; Rotarix) was developed from G1 rotavirus strain 89-12. A trial in Finland showed efficacy comparable with that of RotaShield, and a larger trial is under way in several European countries. In the first epidemic season, vaccine efficacy was 73% against any and 90% against severe rotavirus (mostly G1) gastroenteritis, according to the Vesikari scale. A large scale safety trial, conducted in Latin America plus Finland, indicated no increased risk of intussusception among recipients of Rotarix compared with placebo. The licensure of Rotarix is in process in the European Union.

Update on rotavirus vaccines

Rotavirus was discovered in 1973, and 10 years later the first report of a rotavirus vaccine clinical trial appeared. This update reviews the epidemiology of rotavirus infections, assesses past and current vaccines and presents ideas for implementation of vaccination programs in developed and developing countries.

Evaluation of safety, immunogenicity and efficacy of an attenuated rotavirus vaccine, RIX4414: A randomized, placebo-controlled trial in Latin American infants

BACKGROUND

A live attenuated monovalent rotavirus vaccine RIX4414 was developed with a human strain of G1P1A P[8] specificity to reduce the rotavirus burden in children.

METHODS

A double blind, randomized, placebo-controlled study evaluated the efficacy, immunogenicity, safety and reactogenicity of 2 oral doses of RIX4414 (10(4.7), 10(5.2) or 10(5.8) focus-forming units) at 2 and 4 months coadministered with routine vaccinations and oral poliovirus vaccine given for study purposes at least 14 days apart. The 2155 infants (1618 vaccine/537 placebo) enrolled in Brazil, Mexico and Venezuela were followed until 1 year of age.

RESULTS

Antirotavirus IgA seroconversion rates 2 months after dose 2 ranged between 61% (10(4.7) ffu group) and 65% (10(5.8) ffu group), and most of the infants had seroprotective levels of antibodies to coadministered routine vaccinations. The reactogenicity profile of RIX4414 was similar to that of the placebo, and no vaccination-related serious adverse events were reported. Protective efficacy against severe and any rotavirus gastroenteritis from 15 days post-dose 2 was highest in the 10(5.8) ffu group [86%; 95% confidence interval (95% CI), 63-96% and 70% (95% CI 46-84%), P < 0.001, 2-sided Fisher's exact test]. The efficacy against hospitalization was 79% (95% CI 48-92%) for pooled vaccine groups. Multiple rotavirus serotypes [G1 (50%), G9 (40%), G2, G3 and G4] were identified from gastroenteritis stools (enzyme-linked immunosorbent assay and reverse transcription-polymerase chain reaction) during the study period. For severe gastroenteritis caused by G9 serotypes, the protection reached 77% (95% CI 18-96%) in the 10(5.8) ffu group, providing proof of concept that the monovalent G1P1A P[8] human rotavirus vaccine elicits cross-protection against the G9 strain. A reduction in any and severe rotavirus gastroenteritis was already observed at post-dose 1 (period: day of dose 1 to 14 days post-dose 2) in vaccinees compared with placebo recipients.

CONCLUSIONS

Two doses of RIX4414 are highly efficacious, providing cross-protection (G1 and G9 strains, prevalent during this study) and early protection against any and severe rotavirus gastroenteritis and hospitalization to infants in Latin America.

Rotavirus Vaccines: Targeting the Developing World

For the past 2 decades, rotavirus infection, the most common cause of severe diarrhea in children, has been a priority target for vaccine development. This decision to develop rotavirus vaccines is predicated on the great burden associated with fatal rotavirus disease (i.e., 440,000 deaths/year), the firm scientific basis for developing live oral vaccines, the belief that increased investment in development at this time could speed the introduction of vaccines in developing countries, and the appreciation that implementation of a vaccine program should result in a measurable decrease in the number of hospitalizations and deaths associated with rotavirus disease within 2-3 years. RotaShield (Wyeth-Ayerst), the first rotavirus vaccine licensed in the United States, was withdrawn after 9 months because of a rare association of the vaccine with the development of intussusception. In the developing world, this vaccine could still have had a measurable effect, because the benefits of preventing deaths due to rotavirus disease would have been substantially greater than the rare risk of intussusception. Two live oral vaccines being prepared by GlaxoSmithKline and Merck have completed large-scale clinical trials. The GlaxoSmithKline vaccine has been licensed in Mexico and the Dominican Republic, and the Merck vaccine could be licensed in the United States within 1 year; several other candidate vaccines are in earlier stages of testing. However, many challenges remain before any of these vaccines can be incorporated into childhood immunization programs in the developing world. First, vaccine efficacy, which has already been demonstrated in children in industrialized and middle-income countries, needs to be proven in poor developing countries in Africa and Asia. The safety of vaccines with regard to the associated risk of intussusception must be demonstrated as well. Novel financing strategies will be needed to ensure that new vaccines are affordable and available in the developing world. Decision makers and parents in developing countries need to know about this disease that has little name recognition and is rarely diagnosed. Finally, for the global effort toward the prevention of rotavirus disease to be successful, special efforts will be required in India, China, and Indonesia, because one-third of all deaths due to rotavirus disease occur in these countries, and because these countries depend almost entirely on vaccines manufactured domestically.

Rotavirus vaccines and the prevention of hospital-acquired diarrhea in children

Rotavirus, the major cause of severe acute dehydrating gastroenteritis in children less than 5 years of age, is responsible for an estimated 20-50% of all hospitalizations for diarrhea and approximately 440,000 deaths annually, primarily in the developing world. Rotavirus vaccines are considered the most promising means for disease prevention. While the prime rationale for developing rotavirus vaccines has been the enormous burden of rotavirus infection leading to severe and fatal disease, a secondary benefit may be the prevention of nosocomial rotavirus diarrhea. We have reviewed the burden of intra-hospital-acquired rotavirus infections from several countries and found that in the United States alone, as many as 25% of rotavirus hospitalizations or approximately 16,000-18,000 hospitalizations each year might be due to rotavirus infections acquired within hospitals. To countries with low rotavirus-associated mortality, prevention of these infections and the resulting economic savings therefore represent an important secondary goal. Several rotavirus vaccines are in development, and two candidates are currently being tested in large-scale safety and efficacy trials. Development of safe and effective rotavirus vaccines will protect children worldwide against the severe consequences of rotavirus infections including prolonged hospitalizations for nosocomially acquired infections.

Rotavirus vaccine for preventing diarrhoea

BACKGROUND

Rotaviruses cause viral gastroenteritis and result in more deaths from diarrhoea in children under 5 years of age than any other single agent, particularly in low- and middle-income countries.

OBJECTIVES

To assess rotavirus vaccines in relation to preventing rotavirus diarrhoea, death, and adverse events.

SEARCH STRATEGY

We searched the Cochrane Infectious Diseases Group's trial register (October 2003), the Cochrane Central Register of Controlled Trials (The Cochrane Library Issue 3, 2003), MEDLINE (1966 to October 2003), EMBASE (January 1980 to October 2003), LILACS (1982 to October 2003), Biological Abstracts (January 1982 to October 2003), reference lists of articles, and contacted researchers and rotavirus vaccine manufacturers.

SELECTION CRITERIA

Randomized controlled trials comparing rotavirus vaccines to placebo, no intervention, or other rotavirus vaccines in children and adults.

DATA COLLECTION AND ANALYSIS

Two reviewers independently extracted data and assessed trial methodological quality, and contacted trial authors for additional information.

MAIN RESULTS

Sixty-four trials provided information on efficacy and safety of three main types of rotavirus vaccine (bovine, human, and rhesus) for 21,070 children. Different levels of efficacy were demonstrated with different vaccines varying from 22 to 89% to prevent one episode of rotavirus diarrhoea, 11 to 44% to prevent one episode of all-cause diarrhoea, and 43 to 90% to prevent one episode of severe rotavirus diarrhoea. Rhesus vaccine demonstrated a similar efficacy against one episode of rotavirus diarrhoea (37 and 44% respectively), and one episode of all-cause diarrhoea (around 15%) for trials performed in high and middle-income countries. Results on mortality and safety of the vaccines were scarce and incomplete. We noticed important heterogeneity among the pooled studies and were unable to discard a biased estimation of effect.

REVIEWER'S CONCLUSIONS

Current evidence shows that rhesus rotavirus vaccines (particularly RRV-TV) and the human rotavirus vaccine 89-12 are efficacious in preventing diarrhoea caused by rotavirus and all-cause diarrhoea. Evidence about safety, and about mortality or prevention of severe outcomes, is scarce and inconclusive. Bovine rotavirus vaccines were also efficacious, but safety data are not available. Trials of new rotavirus vaccines will hopefully improve the evidence base. Randomized controlled trials should be performed simultaneously in high-, middle-, and low-income countries.

Rotavirus strains circulating in Africa during 1996-1999: emergence of G9 strains and P[6] strains

Rotavirus infection is associated with 150000-200000 deaths annually in Africa. Although the withdrawal of the RotaShield vaccine has been a major setback in rotavirus vaccine development, new vaccine candidates are under development and approaching phase II and III trials. Before these trials could be conducted in Africa, a comprehensive survey of the circulating VP7 serotypes and VP4 genotypes is required. During the past 3 years, over 3000 rotavirus-positive specimens from several African countries have been analysed. RT-PCR techniques for the VP7 and VP4 genotypes and by monoclonal antibodies to the VP6 subgroup and VP7 serotype have been performed. Almost 75% of the strains were typed by the VP7 monoclonal antibodies or RT-PCR. VP4 genotyping was done in approximately half of these strains. The predominant strains circulating across Africa during 1996-1999 were P[6]G1 and P[6]G3 strains. Geographic differences were noted and West Africa displayed the most diverse strains with G3/8 and G1/3 "mosaic" viruses occurring commonly. G9 strains were identified in several countries indicating that the strain is emerging in Africa too. G9 was the predominant strain in certain countries during 1999. The circulating types observed will have implications for the new rotavirus vaccine candidates.

Sequence analysis of the VP4, VP6, VP7, and NSP4 gene products of the bovine rotavirus WC3

The bovine rotavirus (BRV) WC3 serves as the background strain in the development of a multivalent reassortant vaccine against rotavirus gastroenteritis in infants. The genes encoding the outer capsid spike protein VP4, the inner capsid protein VP6, the outer capsid glycoprotein VP7, and the viral enterotoxin NSP4 of BRV WC3 were sequenced. Comparative analysis of the deduced amino acids of the sequenced genes indicated that the BRV WC3 strain shares a high degree of amino acid identity with serotype P7 VP4 (93-96%), serotype G6 VP7 (91-97%), subgroup (SG) I VP6 (96-99%), and NSP4 genogroup A (96-98%) BRV strains. Our results confirm and extend previous studies which suggested that the VP4 of BRV WC3 was closely related to that of the P7 prototype, BRV UK. In addition, the VP6 and VP7 of BRV WC3 were very similar to the VP6 and VP7 of both SG I and G6 BRV NCDV and UK strains. However, the NSP4 of BRV WC3 was more closely related to that BRV NCDV, the P6 prototype, than to that of BRV UK.

Clinical evaluation of a single oral dose of human-bovine (UK) reassortant rotavirus vaccines Wa x UK (P1A[8],G6) and Wa x (DS-1 x UK) (P1A[8],G2)

The safety, infectivity, and immunogenicity of two human-bovine reassortant rotavirus candidate vaccines were evaluated in adults, children, and infants. One of these, Wa x UK, contained a single human rotavirus gene from the Wa strain that encoded VP4 P1A specificity in a background of 10 bovine genes including the VP7 gene that encodes G6 specificity, whereas the other, Wa x (DS-1 x UK), possessed the human rotavirus VP4 gene from the Wa strain as well as the human VP7 gene from strain DS-1 that encoded G2 specificity. Each of these vaccines appeared to be well-tolerated and immunogenic in infants less than 6 months of age following a single oral dose, and therefore should be evaluated further as vaccine candidates.

Safety and immunogenicity of tetravalent rhesus-based rotavirus vaccine in Bangladesh

BACKGROUND

Rotavirus is the most common cause of severe gastroenteritis among children worldwide.

OBJECTIVES

To compare the safety, immunogenicity and shedding patterns of rhesus rotavirus (RRV)-tetravalent vaccine vs. placebo among infants in rural Bangladesh.

METHODS

A double blinded, placebo-controlled trial was conducted in which infants (n = 120) were randomly assigned to receive three doses of either vaccine or placebo administered at approximately 6, 10 and 14 weeks of age together with routine immunizations. Data on possible adverse effects of vaccinations were collected daily for 7 days after each dose. Stool samples were collected after each dose, and serum samples were obtained before the first and after the third vaccination.

RESULTS

Fever (> or = 38 degrees C), as measured by study assistants, was noted more frequently among vaccinees (15%) than among placebo recipients (2%) during the 7 days after vaccination but was not reported more frequently by parents of vaccinees vs. placebo recipients. Overall 87% of vaccinees had an antibody response (measured by IgA or anti-RRV-neutralizing antibodies) after vaccination compared with 32% of placebo recipients. Rates of seroconversion were higher among subjects with lower levels of prevaccination antibodies and those who shed rotavirus after vaccination. Vaccine strain viruses were detected in stools from placebo vaccine recipients who had evidence of IgA seroconversion.

CONCLUSIONS

In this population RRV-tetravalent vaccine was comparably immunogenic and safe as in trials conducted in developed countries, where this vaccine has been proved effective in preventing severe rotavirus diarrhea. These data support continued evaluation of rotavirus vaccines in developing countries.

Rotavirus vaccine and intussusception. Where do we go from here?

Since the discovery of rotavirus in 1973, vaccine technology has moved from the use of monovalent attenuated animal rotavirus strains to the development of multivalent human-animal reassortment vaccines. The first licensed vaccine, a rhesus-human tetravalent vaccine, was licensed in 1998. This vaccine was withdrawn from the market a year later when it was noted that administration of vaccine was associated with an increased risk of intussusception. The future of rotavirus vaccine is dependent on the reasons for this association that have yet to be discovered.