Vaccine Reasortment of Rotavirus – Vaccine Creating New Strains
Vaccine or vaccine-reassortant rotavirus strains were detected in fecal specimens from 5 of 106 (4.7%) immunocompetent children who required treatment for rotavirus gastroenteritis at a large pediatric hospital in Texas in 2009–2010. Four strains were related to pentavalent rotavirus vaccine, whereas one was related to monovalent rotavirus vaccine. The contribution of these strains to each patient’s illness was unclear given that 2 patients had prominent respiratory symptoms and 2 were concurrently infected with another pathogen (group F adenovirus and norovirus). Continued monitoring is necessary to assess the role of vaccine strains and vaccine-reassortant strains in pediatric rotavirus infections.
Following vaccination, rotavirus vaccine strains replicate in the gastrointestinal tract and may be shed in the stool. In prelicensure trials and 1 postlicensure assessment, viral shedding was observed 7 days after the first dose in 25.6%–26.5% of RV1 recipients and in 8.9%–21.4% of RV5 recipients 1–15 days after any dose [4–6]. Likely transmission of vaccine virus from infants given RV1 to their unvaccinated twins was observed in a randomized clinical trial [7]. Transmission of RV5 virus through fecal shedding has not been formally assessed; however, 1 instance of horizontal transmission of vaccinederived virus to an unvaccinated sibling resulting in acute gastroenteritis (AGE) requiring medical attention has been described [8].
Rotavirus has the ability to undergo reassortment with wild-type or vaccine-derived strains because of its segmented genome [9]. Little is known about the frequency with which reassortment occurs or the resulting clinical outcome. This report describes 5 children with AGE who were found to be shedding rotavirus vaccine strains and/or vaccine-reassortant strains during routine surveillance.
