LAUSR

Key Points Question What are risk factors for severe breakthrough SARS-CoV-2 infections among vaccinated individuals? Findings In this cohort study of 110 760 vaccinated US veterans, increasing age was most strongly associated with severe disease, with risk increasing steadily among patients older than 50 years. Immunocompromising conditions and comorbidities indicating chronic heart, lung, kidney, or neurologic damage also increased risk, with a magnitude similar to or less than a 10-year age increase. Meaning Identification of the risk factors for severe breakthrough COVID-19 could be used to guide policies and decision-making about preventive measures for those who remain at risk of disease progression despite vaccination.