Rotavirus Genotypes Circulating in Ontario, Canada, Before and After the Implementation of the Immunization Program, 2010-2013

Abstract

Abstract BACKGROUND: Rotavirus A is a common cause of acute gastroenteritis in young children and a significant cause of death worldwide. Rotavirus shows an impressive genetic diversity and its epidemiological surveillance is typically conducted with a binary genotyping system using two major outer capsid antigenic protein genes: G (VP7 gene) and P (VP4 gene). Ontario introduced a publicly funded vaccination program for two and four month old infants for rotavirus in August 2011, using Rotarix® (GlaxoSmithKline), a live monovalent oral vaccine which contains an attenuated G1P[8] strain. Rotavirus vaccination has diminished the magnitude of rotavirus seasons in many countries but it is unclear if it will contribute to selective pressure and increase the prevalence of other genotypes. OBJECTIVES: Our aim was to describe circulating rotavirus genotypes before and after the implementation of Ontario’s immunization program. We monitored the potential change in relative proportions and emergence of rotavirus genotypes in Ontario after vaccination-program implementation. DESIGN/METHODS: Rotavirus detection was conducted at a public health laboratory using electronic microscopy, immunochromatographic testing, and/or laboratory developed multiplex rRT-PCR. A convenience sample of rotavirus positive stool specimens collected in children and adults in Ontario from September 2010 to June 2013 were genotyped using heminested genotyping multiplex PCR. We also searched Pubmed in November 2015 for articles published on rotavirus G10 since 2008. RESULTS: Of the 332 stool specimens collected, we found a decrease in the number of rotavirus positive specimens available for genotyping in the 23 month period post-vaccination (128 specimens) compared to the 11 month period pre-vaccination (204 specimens) in Ontario. We also found an increase in the proportion of genotype G10 in the post-vaccination period (37/128 = 29%) compared to the pre-vaccination period (11/204 = 5%). These G10 specimens originated from different regions of Ontario. Our literature review estimated that only approximately two hundred G10-positive human stool samples were reported from 14 different countries worldwide since 2008. CONCLUSION: Our study showed a decrease in the number of rotavi-rus positive convenience samples after vaccination-program implementation. We also found an unexpected increase of the proportion of rotavirus G10 after the introduction of the immunization program. Genotype G10 is uncommon in human and vaccine effectiveness for this genotype is unclear.Ongoing monitoring of rotavirus prevalence and circulating genotypes is important to study the long-term effect of vaccination and evaluate if this increase in proportion of genotype G10 is representative or persists in Ontario, or is present in other Canadian provinces or countries.