Direct and Indirect Effects of Rotavirus Vaccination Upon Childhood Hospitalizations in 3 US Counties, 2006–2009

Abstract

Background. Routine rotavirus vaccination of US infants began in 2006. We conducted active, population-based surveillance for rotavirus gastroenteritis hospitalizations in 3 US counties to assess vaccine impact. Methods. Children Results. Compared with 2006, a significant reduction in rates of hospitalization for rotavirus infection (P < .001) was observed in 2008 among all age groups. There was an 87% reduction in the 6–11-month-old age group (coverage, 77%), a 96% reduction in the 12–23-months-old age group (coverage, 46%), and a 92% reduction in the 24–35-month-old age group (coverage, 1%), which exceeded reductions expected on the basis of coverage and vaccine effectiveness estimates. Age-specific rate reductions were nearly equivalent to those expected on the basis of age-specific vaccine coverage in 2009. Predominant strains varied annually: G1P[8] (91%) in 2006; G1P[8] (45%) and G12P[8] (36%) in 2007; G1P[8] (89%) in 2008; and G3P[8] (43%), G2P[4] (34%), and G9P[8] (27%) in 2009. Conclusions. Rotavirus vaccination has dramatically decreased rates of hospitalization for rotavirus infection among children in these US counties. In 2008, reductions were prominent among both vaccine-eligible age groups and older, largely unvaccinated children; the latter likely resulted from indirect protection. Although rates among age groups eligible for vaccination remained low in 2009, indirect benefits disappeared.