City-wide school-located influenza vaccination: a retrospective cohort study

Benjamin-Chung, J.; Arnold, B. F.; Mishra, K.; Kennedy, C. J.; Nguyen, A.; Pokpongkiat, N. N.; Djajadi, S.; Seth, A.; Klein, N. P.; Hubbard, A. E.; Reingold, A.; Colford, J. M.

Background: We measured the effectiveness of a city-wide school-located influenza vaccination (SLIV) program implemented in over 102 elementary schools in Oakland, California. Methods: We conducted a retrospective cohort study among Kaiser Permanente Northern California (KPNC) members of all ages residing in either the intervention or a multivariate-matched comparison site from September 2011 - August 2017. Outcomes included medically attended acute respiratory illness (MAARI), influenza hospitalization, and Oseltamivir prescriptions. We estimated difference-in-differences (DIDs) in 2014-15, 2015-16, and 2016-17 using generalized linear models and adjusted for race, ethnicity, age, sex, health plan, and language. Results: Pre-intervention member characteristics were similar between sites. Among school-aged children, SLIV was associated with lower Oseltamivir prescriptions per 1,000 (DIDs: -3.5 (95% CI -5.5, -1.5) in 2015-16; -4.0 (95% CI -6.5, -1.6) in 2016-17) but not with other outcomes. SLIV was associated with lower MAARI per 1,000 in adults 65+ years (2014-15: -13.2, 95% CI -23.2, -3.2; 2015-16: -21.5, 95% CI -31.1, -11.9; 2016-17: -13.0, 95% CI -23.2, -2.9). There were few significant associations with other outcomes among adults. Conclusions: A city-wide SLIV intervention was associated with lower Oseltamivir prescriptions in school-aged children and lower MAARI among people over 65 years, suggesting possible indirect effects of SLIV among older adults.