Evidence of Herd Immunity and Sustained Impact of Rotavirus Vaccination on the Reduction of Rotavirus-Related Medical Encounters Among Infants from 2006 through 2011 in the United States

BACKGROUND:Rotavirus (RV) is the leading cause of severe acute gastroenteritis among young children. Since the US licensure of the pentavalent RV vaccine (RV5) and the monovalent RV vaccine (RV1), a decline of RV activity has been observed. OBJECTIVE:To describe patterns of RV-related health care utilization among infants receiving RV vaccines (RVVs). METHODS:A large national health insurance claims database was used to identify infants born from January 2002 through July 2011. From this cohort, infants were divided into three groups(1) those who received a RVV, (2) those receiving a diphtheria, tetanus, and acellular pertussis (DTaP) vaccine before the introduction of RVV (February 2006), and (3) those receiving DTaP without a concurrent RVV during the period of RVV availability. Study outcomes were rotavirus gastroenteritis (RGE) and acute gastroenteritis. Longitudinal, seasonal RGE incidence patterns among the RVV cohort (n = 140,952) were compared with the referent DTaP-vaccine cohort (n = 131,529). RESULTS:More than 91% of administered RVV were RV5. Mean peak incidence of RV medical encounters in RV-vaccinated infants was 95–96% lower than among DTaP-vaccinated infants who did not receive RVV. RGE incidence among the non–RV-vaccinated DTaP recipients in the RVV-available period (110 per 100,000 infants) was lower than among DTaP recipients in the pre-RVV period (151 per 100,000 infants). The highest RGE incidence in the 2007–2011 period was among older non–RV-vaccinated infants. CONCLUSIONS:Analysis of a national medical claims database indicates a sustained and substantial decrease in the seasonal RV medical claims pattern after the introduction of RVV. This analysis also reveals evidence of herd immunity, although unvaccinated infants continue to be at risk and contribute to smaller seasonal peaks in RV disease activity.