Reactogenicity and immunogenicity of rotavirus WC3 vaccine in 5-12 month old infants

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.

Histo-blood group antigens and rotavirus vaccine shedding in Nicaraguan infants

ABO, Lewis and secretor histo-blood group antigens (HBGA) are susceptibility factors for rotavirus in a P-genotype dependent manner and can influence IgA seroconversion rates following rotavirus vaccination. To investigate the association between HBGA phenotypes and rotavirus vaccine shedding fecal samples (n = 304) from a total of 141 infants vaccinated with Rotarix (n = 71) and RotaTeq (n = 70) were prospectively sampled in three time frames (≤3, 4–7 and ≥8 days) after first vaccination dose. Rotavirus was detected with qPCR and genotypes determined by G/P multiplex PCR and/or sequencing. HBGAs were determined by hemagglutination and saliva based ELISA. Low shedding rates were observed, with slightly more children vaccinated with RotaTeq (19%) than Rotarix (11%) shedding rotavirus at ≥4 days post vaccination (DPV). At ≥4 DPV no infant of Lewis A (n = 6) or nonsecretor (n = 9) phenotype in the Rotarix cohort shed rotavirus; the same observation was made for Lewis A infants (n = 7) in the RotaTeq cohort. Putative in-vivo gene reassortment among RotaTeq strains occurred, yielding mainly G1P[8] strains. The bovine derived P[5] genotype included in RotaTeq was able to replicate and be shed at long time frames (>13 DPV). The results of this study are consistent with that HBGA phenotype influences vaccine strain shedding as similarly observed for natural infections. Due to the low overall shedding rates observed, additional studies are however warranted.

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.

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.

Rotavirus vaccine studies in Europe

Following the discovery and recognition of rotavirus as an important human enteropathogen, work towards the development of rotavirus vaccines was begun in the USA and Europe. The first candidate rotavirus vaccine was launched by SmithKline-RIT, Belgium, and studied in clinical trials in Finland, Yugoslavia, Italy, Switzerland, Austria and the UK. Efficacy trials in Finland of RIT 4237 strain live oral bovine rotavirus vaccine resulted in some fundamental findings about rotavirus immunity in humans: protection against disease rather than infection; better protection against severe than mild disease and heterotypic rather than homotypic protection. Another bovine rotavirus vaccine, strain WC-3, was studied briefly in France. Also studies of rhesus rotavirus vaccine were started early in Europe, and efficacy studies were carried out in Finland and Sweden. Recently, rhesus-human re-assortant tetravalent (RRV-TV) rotavirus vaccine was tested in a field trial in Finland this study was pivotal for the registration of the vaccine in the USA and European Union countries. Despite extensive experience with rotavirus vaccines in Europe, the need for such vaccines in many European countries still requires further assessment.

WC3 reassortant vaccines in children

Bovine rotavirus strain WC3 (P7[5], G6) administered at the 12th passage level was well tolerated clinically in infants and efficiently induced serum virus neutralizing antibody (VNA) with bovine rotavirus G6 specificity. The protective efficacy of WC3 vaccine against all rotavirus disease was inconsistent, varying in four separate trials from 76% to 0%; some selective protection against severe disease was seen in all trials. WC3 reassortants containing the gene for an individual human rotavirus VP7 (G) or VP4 (P) surface antigen were also well tolerated, but preferentially induced VNA to the WC3 parent. Efficacy trials of human G1 VP7 reassortant WI79-9 (P7[5], G1) consistently led to > 60% protection against all rotavirus disease. A quadrivalent WC3 reassortant vaccine was developed to contain four separate monovalent reassortants expressing human rotaviruses surface proteins G1, G2, G3, and P1A [8] respectively. In a multicenter trial including 439 infants, this vaccine induced 67.1% protection against all rotavirus disease (defined as positive for rotavirus antigen by ELISA only [p = < 0.001]) and 72.6% protection when the standard for rotavirus diagnosis was a positive test of stool for both rotavirus antigen by ELISA and rotavirus RNA by electropherotype analysis (p = < 0.001). In this trial, episodes of the most severe rotavirus disease (clinical severity score > 16.0 eight cases) occurred only in placebo recipients.

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

The safety and efficacy of a WC3 rotavirus vaccine was evaluated in a double-blind placebo-controlled trial involving 472 children in Bangui (Central African Republic). Each child received two doses of either placebo (235 children) or vaccine (237 children) at a 1-month interval, the first dose being given at 3 months of age. During the follow-up survey 9 months after the first dose, 117 rotavirus diarrhoeas were observed, 59 in the placebo group, 58 in the vaccinated group. The only positive effect of the vaccine was a significantly higher proportion of mild rotavirus diarrhoeal episodes in the vaccinated group than in the placebo group. Of the children in the vaccinated group, 60% had a positive immune response to WC3 rotavirus when tested by plaque reduction seroneutralization.

Sequential rotavirus infections: characterization of serotypes and electrophoretypes

Few studies have characterized the rotaviruses observed in repeated infections in the same patient. Rotavirus serotypes and electrophoretypes were determined from faecal samples of 24 children hospitalized between 1984 and 1989 in a Clermont-Ferrand hospital and who had had repeated rotavirus shedding. The patients were aged between 3 days and 4 years. Fifty infections were recorded. Of the 48 serotypes obtained, 18 were serotype 1 (37.5%), 10 serotype 2 (20.8%) and 20 serotype 4 (41.7%). Serotype 3 was not found. Seven serotype 2 infections were characterized during rehospitalization. Six patients had two subsequent infections with the same serotype.