Effectiveness of Pentavalent Rotavirus Vaccine Against a Diverse Range of Circulating Strains in Nicaragua

Background. Because >60 rotavirus strains have been reported worldwide, concerns exist about strain replacement after the introduction of rotavirus vaccines, particularly in developing countries with diverse strains and lower efficacy. Methods. We used the case-control design in 4 hospitals in Nicaragua to assess strain-specific vaccine effectiveness (VE) of a pentavalent rotavirus vaccine (RotaTeq) against rotavirus diarrhea. Cases were identified through prospective strain surveillance with reverse transcription-polymerase chain reaction for 3 years among children hospitalized for diarrhea, and controls were children negative for rotavirus. Results. We enrolled 1178 case-patients, 1082 (92%) with G and P typing, and 4927 controls. A different strain predominated each year with increasing age of the vaccine-eligible cohort during the study period: G2P[4] in 2008 (97%; mean age, 11.9 months), G1P[8] in 2009 (55%; mean age, 17.0 months), and G3P[8] in 2010 (78%; mean age, 17.3 months). Overall VE was 45% (95% confidence interval, 25%-59%). Regardless of the strain, VE estimates were 12%-79% lower among children aged ≥12 months relative to those 6-11 months of age. The lower VE for G3P[8] was related to the higher mean age of cases (17.3 months) compared with the G2P[4] strains (11.9 months), with a significant trend (R² = 0.819; P <. 001) of declining effectiveness with increasing mean age of the cases. Conclusions. Introduction of RotaTeq did not result in sustained emergence of any particular strain in Nicaragua. Variation in strain-specific effectiveness was due to an age-related decline in effectiveness rather than differences in protection against the observed strains.