1715. Influenza-like Illness (ILI) Experience Among Healthcare Workers in Military Treatment Facilities: An Offshoot of the Pragmatic Assessment of Influenza Vaccine Effectiveness in the DoD (PAIVED) Study

Abstract

Background. Healthcare workers (HCWs) are at heightened risk of exposure to respiratory pathogens. There are limited published data on influenza-like illness (ILI) experience among HCWs, and the few available studies were hampered by incomplete vaccination histories. PAIVED, a multicenter, multiservice study assessing influenza vaccine effectiveness in the Department of Defense, provides a unique opportunity to describe ILI experience among vaccinated HCWs compared to vaccinated non-HCWs. Methods. PAIVED participants were randomized to receive either egg-based, cell-based, or recombinant-derived influenza vaccine then surveyed weekly for ILI. At enrollment, participants provided key demographic data including whether they were HCWs with direct patient contact. ILI was defined a priori as 1) having cough or sore throat plus 2) feeling feverish/having chills or having body aches/fatigue. Participants with ILI completed a daily symptom diary for seven days and submitted a nasal swab for pathogen detection. Results. Of 4433 eligible participants enrolled during the 2019-20 influenza season, 1551 (35%) were HCWs. A higher percentage of HCWs experienced an ILI than non-HCWs (34% vs 26%, p< 0.001). Overall, HCWs were more likely to be female (42% vs 32%), age 25-34 years (39% vs 28%), active-duty military (81% vs 62%), non-smokers (88% vs 75%), and physically active (92% vs 85%). Self-reported race differed between HCWs and non-HCWs; a higher proportion of HCWs identified as White (63% vs 56%) or Asian (8% vs 5%). Similar demographic differences existed among HCWs and non-HCWs with ILI. HCWs were more likely to respond to at least 50% of weekly surveillance messages, irrespective of ILI status. HCWs with ILI had less severe lower respiratory symptoms (p< 0.001) and a shorter duration of illness (12.4±8.1 days vs 13.7±9.0, p=0.005) than non-HCWs. Pathogen data is pending. Conclusion. HCWs in PAIVED were more likely to report ILI than their non- HCW counterparts yet tended to have lower illness severity, possibly reflecting a higher level of baseline health or enhanced awareness of early ILI symptoms. The important epidemiologic position HCWs occupy for ILI has been apparent in the COVID-19 pandemic. Exploring ways to mitigate ILI risk in HCWs beyond influenza vaccination is warranted.