Rotavirus Vaccine is Effective Against Rotavirus Gastroenteritis Resulting in Outpatient Care: Results from the MAAGE Study.

BACKGROUND Rotavirus is a common cause of severe pediatric acute gastroenteritis (AGE). Two vaccines are licensed in the United States and have demonstrated high effectiveness against moderate to severe disease. However, fewer data are available on rotavirus vaccine effectiveness (VE) against milder disease. METHODS We leveraged active surveillance data from Kaiser Permanente Northwest (KPNW) to calculate rotavirus VE against medically attended rotavirus illness among age-eligible children. We utilized a test-negative case-control design and applied 4 distinct case definitions based on reverse-transcription-quantitative real-time PCR (qRT-PCR) assay and enzyme immunoassay (EIA) test results. VE was calculated as 100*(1 - Odds Ratio), and models were adjusted for age group. RESULTS The VE analysis population comprised 842 children, 799 (95%) of which had mild disease requiring at most a clinic visit, and 698 (83%) of whom were fully vaccinated against rotavirus. Age-adjusted VE was 70% (95% confidence interval [CI]: 37 - 86%) against disease defined solely by qRT-PCR results, 72% (95% CI: 31 - 89%) against disease as defined by qRT-PCR with a quantification cycle (Cq) value <27, 73% (95% CI: 32 - 90%) against disease that was qRT-PCR positive but EIA negative, and 62% (95% CI: -20 - 88%) against disease defined solely by EIA. Results were similar when restricting to disease resulting in at most an ambulatory clinic or emergency department visit. CONCLUSIONS These results support the effectiveness of rotavirus vaccination in protecting U.S. children from mild to moderate as well as severe disease. Our findings are also useful to show the effectiveness of rotavirus vaccination against qRT-PCR-defined illness.