Resident Factors Associated with Breakthrough SARS-CoV-2 Infections

ABSTRACT

Objective To examine incidence of and resident characteristics associated with BTIs and severe illness among residents with two mRNA vaccinations. Design Retrospective cohort study Setting and Participants Nursing home (NH) residents who completed their primary series of mRNA COVID-19 vaccination by March 31, 2021. Methods Electronic health records and Minimum Data Set assessments from a multi-state NH data consortium were used to identify BTI and severe illness (a composite measure of hospitalization and/or death within 30 days of BTI) occurring prior to November 24, 2021. A t-test for differences in means was used to compare covariates for residents with and without BTI. Finally, we estimated incidence-rate ratios (IRRs) for BTI with 95% confidence intervals (CI) using a modified Poisson regression approach, comparing residents with BTI vs. residents without. We adjusted for facility-fixed effects in our model. Results Our sample included 23,172 residents from 984 NHs who were at least 14 days past their second mRNA vaccine dose. Of those, 1,173 (5%) developed an incident COVID-19 BTI (mean follow-up time 250 days). Among residents with BTI, 8.6% were hospitalized or died within 30 days of BTI diagnosis. Factors associated with severe illness included age 85 years and older (IRR=2.08 [95% CI 1.08-4.02], reference age <65 years), bowel incontinence (IRR=1.73 [95% CI 1.01-2.99]), coronary artery disease (IRR 1.96 [95% CI 1.31-2.94]), chronic kidney disease (IRR 1.65 [95% CI 1.07-2.54]), and schizophrenia (IRR 2.38 [95% CI 1.19-4.75]). Conclusions and Implications Among vaccinated NH residents, BTIs and associated severe illness are rare. Residents aged 85 years and older and with certain comorbidities appear to be the most vulnerable. Given that the pandemic continues and testing policies have relaxed, this data provides prognostic information for NH facilities faced with continued outbreaks.