Real-world impact of vaccination on COVID-19 incidence in health care personnel at an academic medical center

Objective: COVID-19 vaccination effectiveness in healthcare personnel (HCP) has been established, however, questions remain about its performance in high-risk healthcare occupations and work locations. We describe the effect of a COVID-19 HCP vaccination campaign on SARS-CoV-2 infection by timing of vaccination, job type, and work location. Methods: A retrospective review of COVID-19 vaccination acceptance, incidence of post-vaccination COVID-19 infection, hospitalization, and mortality among 16,156 faculty, students, and staff at a large academic medical center was conducted. Data were collected 8 weeks prior to the start of Phase 1a vaccination of frontline employees and ended 11 weeks after campaign completion. Results: COVID-19 employee incidence rate at our institution decreased from 3.2% during the 8 weeks prior to the start of vaccinations to 0.38% by four weeks after campaign initiation. SARS-CoV-2 infection risk was reduced among individuals receiving a single vaccination (HR = 0.52 [0.40, 0.68], p<0.0001) and further reduced with 2 doses of vaccine (HR = 0.17 [0.09, 0.32], p<0.0001). By two weeks after the second dose, the observed case positivity rate was 0.04%. Among Phase 1a HCP, we observed a lower risk of SARS-CoV-2 infection among physicians and a trend toward higher risk for respiratory therapists independent of vaccination status. Rates of infection were similar in a sub-group of nurses when examined by work location. Conclusions: Our findings show the real-world effectiveness of COVID-19 vaccination in HCP. Despite these encouraging results, unvaccinated HCP remain at an elevated risk of infection highlighting the need for targeted outreach to combat vaccine hesitancy.