Effect of rotavirus vaccine on reducing acute gastroenteritis in a large outpatient pediatric network.

Objectives: To measure the effect of rotavirus vaccine (RVV) on acute gastroenteritis (AGE) managed by primary care physicians in the first 2 rotatvirus seasons following the introduction of RVV.

Design: Retrospective cohort study.

Setting: Practice-based network composed of 33 ambulatory pediatric practices in Philadelphia, Pennsylvania.

Participants: All children born from February 22, 2006 (date of RVV licensure), through February 29, 2008, and who received care at any network site.

Main Exposure: Receipt of RVV.

Outcome Measures: The primary outcomes were AGE-related office visits, telephone calls, and episodes (composite outcome consisting of all visits and calls within a 10-day period).

Results: Rates of AGE visits in the 2 rotavirus seasons following the introduction of RVV steadily decreased from 3.0 AGE visits per 100 total office visits in the 2005 season to 1.8 in the 2008 season. In 2007, vaccinations were administered to 9351 of 13 951 vaccine-eligible children (67.0%), and in 2008, they were administered to 9958 of 10 728 (92.8%). Among RVV-immunized children in 2007, AGE calls and episodes were significantly reduced with vaccine effectiveness of 53% and 46%, respectively. No significant difference was seen between RVV-immunized and RVV-nonimmunized children for any outcome in 2008.

Conclusions: Rotavirus vaccine was associated with a significant reduction in outpatient AGE calls and episodes among immunized children in our network in 2007. Despite a reduction in winter AGE rates in the network, no difference was detected between RVV-immunized and RVV-nonimmunized children for any outcome in 2008. Further study is needed to understand the lack of vaccine effect in 2008.