Distribution of rotavirus genotypes causing nosocomial and community-acquired acute gastroenteritis at the Children's Hospital of Philadelphia in the new rotavirus vaccine era

Rotavirus infections in Detroit, USA, a region of low vaccine prevalence

After a sharp drop of rotavirus (RV) infections at Children's Hospital of Michigan, Detroit, USA in 2010 season, we noted an increase in the number of cases during the 2011 season including some RV vaccine (RVV) recipients. This study was conducted to determine the circulating genotypes during 2011 season and whether the increase in RV diarrhea was caused by replacement genotypes. G and P genotypes were determined by RT PCR and nucleotide sequencing of selected strains was performed. The vaccination rate among study patients was 24 %. RV strains from 68 stool samples were genotyped including 18 from vaccinated children and 50 from unvaccinated children. The predominant G genotype was G1 (58.8 %) followed by G9 (17.7 %) and G4 (15.5 %). P[8] was the predominant P genotype (68 %) followed by P[6] (17.6 %) and P[4] (3 %). All G9 strains were associated with P[6]. The most prevalent G-P combination was G1P[8] (56 %), followed by G9P[6] (17.6 %). Similar proportions of RV genotypes were found among vaccinated and unvaccinated children. Our local data suggest that 5 years after the introduction of RVV there has been no genotype replacement. Although a small increase in G9P[6] frequency was noted, G1P[8] remained the predominant strain of RV in our inner city community in the Midwestern USA.

Review of global rotavirus strain prevalence data from six years post vaccine licensure surveillance: is there evidence of strain selection from vaccine pressure?

Comprehensive reviews of pre licensure rotavirus strain prevalence data indicated the global importance of six rotavirus genotypes, G1P[8], G2P[4], G3P[8], G4P[8], G9P[8] and G12P[8]. Since 2006, two vaccines, the monovalent Rotarix (RV1) and the pentavalent RotaTeq (RV5) have been available in over 100 countries worldwide. Of these, 60 countries have already introduced either RV1 or RV5 in their national immunization programs. Post licensure vaccine effectiveness is closely monitored worldwide. This review aimed at describing the global changes in rotavirus strain prevalence over time. The genotype distribution of the nearly 47,000 strains that were characterized during 2007-2012 showed similar picture to that seen in the preceding period. An intriguing finding was the transient predominance of heterotypic strains, mainly in countries using RV1. Unusual and novel antigen combinations continue to emerge, including some causing local outbreaks, even in vaccinated populations. In addition, vaccine strains have been found in both vaccinated infants and their contacts and there is evidence for genetic interaction between vaccine and wild-type strains. In conclusion, the post-vaccine introduction strain prevalence data do not show any consistent pattern indicative of selection pressure resulting from vaccine use, although the increased detection rate of heterotypic G2P[4] strains in some countries following RV1 vaccination is unusual and this issue requires further monitoring.

Group A rotavirus universal mass vaccination: how and to what extent will selective pressure influence prevalence of rotavirus genotypes?

Two human group A rotavirus (RVA) vaccines are available and highly effective in preventing severe gastroenteritis caused by all commonly circulating human RVA genotypes. The effect of universal mass vaccination on the RVA genotype distribution is discussed based on the knowledge of complete RVA genotype constellations, data from clinical efficacy trials and effectiveness studies, and genotype surveillance data from countries with universal mass vaccination programs. The theoretically predicted relative enrichment of RVA strains with the G2P[4] DS-1-like genotype constellation in regions with high coverage by Rotarix(®) (GlaxoSmithKline Biologicals, Rixensart, Belgium) seems to become apparent. A G3P[8] genotype increase, which was noted in several regions with a high coverage of RotaTeq(®) (Merck and Co., Inc., NJ, USA), is more difficult to explain based on the theoretical considerations.

A critical literature review of health economic evaluations of rotavirus vaccination

Two licensed vaccines are available to prevent RVGE in infants. A worldwide critical review of economic evaluations of these vaccines was conducted. The objective was to describe differences in methodologies, assumptions and inputs and determine the key factors driving differences in conclusions. 68 economic evaluations were reviewed. RV vaccination was found to be cost-effective in developing countries, while conclusions varied between studies in developed countries. Many studies found that vaccination was likely to be cost-effective under some scenarios, such as lower prices scenarios, inclusion of herd protection, and/or adoption of a societal perspective. Other reasons for variability included uncertainty around healthcare visits incidence and lack of consensus on quality of life (QoL) valuation for infants and caregivers. New evidence on the vaccination effectiveness in real-world, new ways of modeling herd protection and assessments of QoL in children could help more precisely define the conditions under which RV vaccination would be cost-effective in developed countries.

Diversity and relationships of cocirculating modern human rotaviruses revealed using large-scale comparative genomics

Group A rotaviruses (RVs) are 11-segmented, double-stranded RNA viruses and are primary causes of gastroenteritis in young children. Despite their medical relevance, the genetic diversity of modern human RVs is poorly understood, and the impact of vaccine use on circulating strains remains unknown. In this study, we report the complete genome sequence analysis of 58 RVs isolated from children with severe diarrhea and/or vomiting at Vanderbilt University Medical Center (VUMC) in Nashville, TN, during the years spanning community vaccine implementation (2005 to 2009). The RVs analyzed include 36 G1P[8], 18 G3P[8], and 4 G12P[8] Wa-like genogroup 1 strains with VP6-VP1-VP2-VP3-NSP1-NSP2-NSP3-NSP4-NSP5/6 genotype constellations of I1-R1-C1-M1-A1-N1-T1-E1-H1. By constructing phylogenetic trees, we identified 2 to 5 subgenotype alleles for each gene. The results show evidence of intragenogroup gene reassortment among the cocirculating strains. However, several isolates from different seasons maintained identical allele constellations, consistent with the notion that certain RV clades persisted in the community. By comparing the genes of VUMC RVs to those of other archival and contemporary RV strains for which sequences are available, we defined phylogenetic lineages and verified that the diversity of the strains analyzed in this study reflects that seen in other regions of the world. Importantly, the VP4 and VP7 proteins encoded by VUMC RVs and other contemporary strains show amino acid changes in or near neutralization domains, which might reflect antigenic drift of the virus. Thus, this large-scale, comparative genomic study of modern human RVs provides significant insight into how this pathogen evolves during its spread in the community.

Genotype constellation and evolution of group A rotaviruses infecting humans

Numerous rotavirus group A (RVA) strains with distinct G-genotype and P-genotype combinations have been described infecting humans worldwide. However, the increasing amount of complete RVA genome data which have become available, suggest that only RVA strains with 2 discrete genotype constellations have been successful in sustaining infection of humans worldwide over longer periods of time. Those genotype constellations have been designated I1-R1-C1-M1-A1-N1-T1-E1-H1 and I2-R2-C2-M2-A2-N2-T2-E2-H2 and are also known as Wa-like and DS-1-like, respectively. RVAs of other genotype constellations which were able to spread to a limited extent in the human population are AU-1-related RVA strains (I3-R3-C3-M3-A3/A12-N3-T3-E3-H3/H6) in combination with G3P[9] or G12P[9], and neonatal G10P[11] RVA strains in India (bovine×human Wa-like reassortants). On the basis of the analysis of complete genomes, it is suggested that the overall genetic diversity of epidemiologically widespread human RVA strains is more limited than generally assumed. This conclusion has consequences for how we look at host range restriction and the criteria according to which the effectiveness of RVA universal mass vaccination programs is assessed.