Evaluation of the impact of rotavirus vaccine on acute care visits, hospitalizations and laboratory testing in Wisconsin, 2002-2008

Rotavirus is a highly communicable virus and the most common cause of severe gastroenteritis among infants and young children in the United States. In February 2006, a new rotavirus vaccine was licensed, and in August 2006 the Advisory Committee on Immunization Practices recommended its routine use in infants. Additionally, a second rotavirus vaccine was licensed in April 2008. To assess the uptake of rotavirus vaccine and evaluate its effect on rotavirus morbidity throughout Wisconsin we analyzed data from the following sources: the population-based Wisconsin Immunization Registry, a statewide hospital inpatient surveillance system, a network of outpatient clinics with 2.4 million outpatient visits during 2002 through 2008, and a network of up to 27 testing sites. By March 2008, 63% of children aged less than 12 months had received the complete series of 3 doses of rotavirus vaccine. Rotavirus hospitalizations (ICD-9=008.61) during January –June 2008 decreased from an annual mean of 418 during 2002-2006 to 66 in 2008 (84% decline). Acute care visits for all-cause diarrheal illness among children aged less than 12 months decreased by 50% in 2008 compared to 2006. While the average number of rotavirus tests conducted weekly has remained relatively constant from 2005 through 2008, the percentage of tests positive for rotavirus decreased by nearly two thirds. The brisk uptake of rotavirus vaccine among Wisconsin's infants appears to have significantly impacted rotavirus morbidity during the first two seasons following licensure of the new vaccines.