Effects of immunizing school children with 2009 influenza A (H1N1) monovalent vaccine on absenteeism among students and teachers in Maine

The overall and indirect effects of immunizing school children with influenza A (H1N1) 2009 pandemic virus vaccine prior to and during the peak of virus circulation were evaluated on student and teacher school absenteeism. We used records collected from late 2009 through early 2010 from schools in four Maine counties. Mixed logistic regression models were used to estimate the daily association between school-level immunization coverage and absenteeism by level of influenza activity, after adjusting for the proportion of students receiving reduced-cost lunches, student minority status, absences adjacent to weekends and Thanksgiving, rural school location, and the circulation of other respiratory viruses. Increasing student immunization coverage was associated with reduced absenteeism during periods of high influenza activity. For example, as immunization coverage during the peak week of pandemic virus circulation increased from 38% to 69% (the 10th and 90th percentiles of observed coverage, respectively), relative reductions in daily absenteeism among all students, unimmunized students, and teachers were 8.2% (95% confidence interval [CI]: 6.5, 9.9), 5.7% (95% CI: 4.2, 7.3), and 8.7% (95% CI: 1.3, 16), respectively. Increased vaccination coverage among school-aged Maine children had modest overall and indirect effects on student and teacher absenteeism, despite vaccination occurring just prior and during peak pandemic virus circulation.