Healthcare Workers Have More Frequent and Less Severe Influenza-Like Illness Than Non-healthcare Workers: Findings From the PAIVED Study

Background. The Pragmatic Assessment of Influenza Vaccine Effectiveness in the Department of Defense (PAIVED) study is a multicenter trial assessing influenza vaccine effectiveness with annual enrollment over 4 consecutive influenza seasons (2018/2019–2021/2022). Data from PAIVED provides an opportunity to evaluate influenza-like illness (ILI) in healthcare workers (HCWs) compared to non-HCWs. Methods. Participants in the PAIVED study were recruited from September to January in each influenza season and received egg-based, cell-based, or recombinant influenza vaccine. If a participant reported an ILI, they submitted a nasal swab for pathogen detection and a symptom diary for 7 days. For this analysis, vaccine groups were pooled and multivariable regression models were performed. Results. Among the 13 959 participants included in this analysis, 35% were HCWs. Healthcare workers were more likely to be female, white, and 25–44 years of age. In addition, HCWs were more likely to report ILIs than non-HCWs (24.1% vs 17.4%, P <.01), and this difference persisted in our multivariable model (RR 1.16 [95% CI 1.08, 1.24]). No statistically significant differences were observed between HCWs and non-HCWs in specific pathogen detection. In terms of ILI severity, HCWs reported 0.28 more days of missed work (95% CI 0.01, 0.55), 0.36 fewer days with fever (−0.60, −0.13), and, in general, reported less severe ILI symptoms in the FLU-PRO diaries. Conclusions. Healthcare workers enrolled in PAIVED reported more ILIs during the study period than non-HCWs, despite all participants receiving influenza vaccination. Further work is needed to reduce the risk of ILIs in HCWs. Clinical Trials Registration. A Pragmatic Assessment of Influenza Vaccine Effectiveness in the DoD (PAIVED): NCT03734237, Study Details | A Pragmatic Assessment of Influenza Vaccine Effectiveness in the DoD | ClinicalTrials.gov.