Evidence of Vaccine-related Reassortment of Rotavirus, Brazil, 2008–2010

Tatiana Lundgren Rose

, Marcelle Figueira Marques da Silva¹, Mariela Martinéz Goméz¹, Hugo Reis Resque, Maria Yury Travassos Ichihara, Eduardo de Mello Volotão, and José Paulo Gagliardi Leite

Author affiliations: Oswaldo Cruz Institute, Rio de Janeiro, Brazil. (T.L. Rose, M.F.M. Silva, M.M. Gomez, H.R. Resque, E. M. Volotão, J.P.G. Leite); Federal University of Bahia, Salvador, Bahia, Brazil (M.Y.T. Ichihara)

Abstract

Analysis of 27 rotavirus strains from vaccinated and unvaccinated children revealed reassortment events in 3 strains: a gene derived from a vaccine; a gene acquired from a circulating strain; and reassortment between circulating strains. Data suggest that the widespread use of this monovalent rotavirus vaccine may introduce vaccine genes into circulating human rotaviruses or vice versa.

Group A rotaviruses (RVAs) are a frequent cause of diarrhea in children. The RVA genome consists of 11 dsRNA segments that encode 6 structural (VP1–VP4, VP6, VP7) and 6 non-structural (NSP1– NSP6) proteins (1). The basis of a new classification system is phylogenetic analysis of 11 RVA genome segments, although binary classification is still used; genotyping is based on the coding genes for VP7 (G) and VP4 (P) (2).
Vaccination is considered effective in reducing the consequences of RVA. Two vaccines, Rotarix (Glaxo SmithKline, Brentford, UK) and RotaTeq (Merck & Co., Whitehouse Station, NJ, USA), are licensed in several countries. Both vaccines demonstrated broad protection against the most common RVA genotypes (3).
In Brazil, Rotarix, a monovalent attenuated human rotavirus vaccine for infants 6–24 weeks of age, was introduced in the National Immunization Programs in March, 2006. The vaccine is delivered in 2 doses, > 4 weeks apart. In 2009, when vaccine coverage achieved 85.9%, reduction in hospitalization associated with diarrhea (17%) and in related mortality rates (22%) was observed (4). This study aimed to assess phylogenetic relationships between G1P[8] RVA obtained from vaccinated and unvaccinated children hospitalized for acute gastroenteritis.