Evaluation of a city-wide school-located influenza vaccination program in Oakland, California, with respect to vaccination coverage, school absences, and laboratory-confirmed influenza: A matched cohort study

Abstract

BackgroundIt is estimated that vaccinating 50%-70% of school-aged children for influenza can produce population-wide indirect effects. We evaluated a city-wide school-located influenza vaccination (SLIV) intervention that aimed to increase influenza vaccination coverage. The intervention was implemented in �95 preschools and elementary schools in northern California from 2014 to 2018. Using a matched cohort design, we estimated intervention impacts on student influenza vaccination coverage, school absenteeism, and community-wide indirect effects on laboratory-confirmed influenza hospitalizations. Methods and findingsWe used a multivariate matching algorithm to identify a nearby comparison school district with pre-intervention characteristics similar to those of the intervention school district and matched schools in each district. To measure student influenza vaccination, we conducted cross-sectional surveys of student caregivers in 22 school pairs (2017 survey, N = 6,070; 2018 survey, N = 6,507). We estimated the incidence of laboratory-confirmed influenza hospitalization from 2011 to 2018 using surveillance data from school district zip codes. We analyzed student absenteeism data from 2011 to 2018 from each district (N = 42,487,816 student-days). To account for pre-intervention differences between districts, we estimated difference-in-differences (DID) in influenza hospitalization incidence and absenteeism rates using generalized linear and log-linear models with a population offset for incidence

Evaluation of a city-wide school-located influenza vaccination program in Oakland, California with respect to race and ethnicity: a matched cohort study

“…We previously reported results from an evaluation of a city-wide SLIV program delivered in elementary schools in Oakland, California from 2014-2018. 20 We found that the intervention was associated with 7-11 percentage points higher vaccination coverage among school-aged children and 17 to 37 lower incidence of influenza hospitalizations per 100,000 during influenza seasons in which a moderately effective vaccine was being used. Here, we investigated whether SLIV effectiveness varied by race/ethnicity in a pre-specified subgroup analysis.…”

“…11 By increasing vaccination coverage, SLIV may contribute to herd immunity and reduce influenza transmission community-wide, which may reduce racial/ethnic disparities in influenza 12,13 . Prior studies reported that SLIV programs were associated with increased influenza vaccination coverage [14][15][16][17][18][19][20] and decreased school absences [14][15][16][17][20][21][22] and student illness [14][15][16][17] , but no studies have measured the differential impacts of large-scale SLIV interventions by race/ethnicity. We previously reported results from an evaluation of a city-wide SLIV program delivered in elementary schools in Oakland, California from 2014-2018.…”

“…Additional program details are reported elsewhere. 20 In the 2014-15 and 2015-16 seasons, the program primarily provided live attenuated influenza vaccines (LAIV), with inactivated injectable influenza vaccine (IIV) available to students with contraindications. In LAIV seasons, the vaccine had relatively low effectiveness against the predominant circulating strain.…”

“…To measure influenza vaccination coverage in the study population, we distributed two cross-sectional surveys in 22 matched school pairs 20 The surveys were conducted independently from the intervention. All students in participating schools were invited to participate in the surveys, regardless of their vaccination status or participation in the SLIV program.…”

“…Pre-intervention trends were similar between sites. 20 We pre-specified stratification by age groups (non-elementary school aged individuals (<= 4 years, >13 years) and older adults (>=65 years)). Because the number of elementary school aged children who were hospitalized for influenza was small, there was inadequate statistical power to estimate associations separately for this age group.…”