Volume 14, Number 5—May 2008
Rotavirus PG2 in a Vaccinated Population, Brazil
To the Editor: Gurgel et al. provide an early examination of postmarketing surveillance data from Brazil, one of the first countries to implement routine childhood immunization with Rotarix vaccine (1). In a community with reported vaccination coverage of 50%, the PG2 strain was detected in all 21 rotavirus-positive stool samples identified during November 2006–February 2007. Although monitoring effectiveness of Rotarix against PG2 strains is of interest (2), the small sample size, short duration of surveillance, and lack of a comparison group preclude firm assessment of an association between PG2 predominance and vaccination.
Because Rotarix was introduced in Brazil in March 2006, most children >12 months old (66 [51%] of 129) in the study were ineligible for vaccination. Genotype PG2 was the only strain identified even in older children, which suggests either a change in disease ecology from vaccination or the random circulation of PG2 strains in the community. Ongoing hospital-based surveillance during 2006 in 3 regional countries that had not introduced rotavirus vaccine (El Salvador, Guatemala, and Honduras) showed that PG2 was the predominant circulating strain (prevalence 68%–81%). Thus, as previously documented (3,4), the predominance of PG2 strains after Rotarix introduction in Brazil could represent a natural shift unrelated to vaccination.
Evaluation of vaccine effectiveness against specific strains will allow full assessment of the public health impact of vaccination. Although the data are sparse in the study from Gurgel et al., a comparison of the odds of vaccination among rotavirus-positive (cases) versus rotavirus-negative (controls) children shows 80% vaccine effectiveness against PG2 strains among infants <1 year of age, in accordance with recently published data from a controlled trial (5). To further elucidate vaccine impact, we are providing support for vaccine effectiveness studies in Nicaragua and El Salvador and conducting strain monitoring before and after licensure throughout Latin America.
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- Glass RI, Parashar UD, Bresee JS, Turcios R, Fischer TK, Widdowson MA, Rotavirus vaccines: current prospects and future challenges. Lancet. 2006;368:323–32.
- Desselberger U, Iturriza-Gomara M, Gray JJ. Rotavirus epidemiology and surveillance. Novartis Found Symp. 2001;238:125–47.
- Santos N, Hoshino Y. Global distribution of rotavirus serotypes/genotypes and its implication for the development and implementation of an effective rotavirus vaccine. Rev Med Virol. 2005;15:29–56.
- Vesikari T, Karvonen A, Prymula R, Schuster V, Tejedor JC, Cohen R, Efficacy of human rotavirus vaccine against rotavirus gastroenteritis during the first 2 years of life in European infants: randomised, double-blind controlled study. Lancet. 2007;370:1757–63.