Abstract
OBJECTIVE: The aim of the study is to identify factors associated with breakthrough infection among a cohort of Midwestern healthcare personnel (HCP). METHODS: SARS-CoV-2-positive test results between March 1, 2020, and July 31, 2021, were collected from electronic medical records of HCP to identify breakthrough infections. RESULTS: Healthcare personnel who were younger than 35 years, received the Pfizer vaccine, and worked in COVID clinical units had greater adjusted odds of breakthrough infection. COVID infection before full vaccination was associated with reduced odds of breakthrough infection. CONCLUSIONS: Our study concluded that the most vulnerable HCP are younger, working in COVID-19 clinical units, and received Pfizer-BioNTech primary series vaccines. Healthcare personnel who had COVID before vaccination were at reduced risk of breakthrough infection, indicating that supplemental immunity could better protect at-risk HCP groups.