Severe COVID-19 outcomes are rare after primary vaccination, but those who are 65 years or older, are immunosuppressed, or have underlying conditions may be at increased risk, according to research published in the Jan. 7 issue of the U.S. Centers for Disease Control and Prevention Morbidity and Mortality Weekly Report .

Christina Yek, M.D., from the National Institutes of Health Clinical Center in Bethesda, Maryland, and colleagues used data from 465 facilities in a large U.S. health care database to examine the frequency of and risk factors for developing a severe COVID-19 outcome after completion of a primary COVID-19 vaccination series (receipt of two doses of BNT162b2 [Pfizer-BioNTech] or mRNA-1273 [Moderna] or a single dose of JNJ-78436735 [Janssen]).

The researchers found that 2,246 of the 1,228,664 persons who completed primary vaccination during December 2020 to October 2021 developed COVID-19 (18.0 per 10,000 vaccinated persons) and 189 had a severe outcome (1.5 per 10,000), 36 of whom died (0.3 per 10,000). Persons who were aged 65 years or older, were immunosuppressed, or had at least one of six other underlying conditions had a higher risk for severe outcomes. All persons with severe outcomes had one or more of these risk factors; of those who died, 77.8 percent had four or more risk factors.

"Even when vaccinated, persons with identifiable risk factors should receive interventions including chronic disease management, precautions to reduce exposure, additional primary and booster vaccine doses, and effective pharmaceutical therapy as indicated to reduce risk for severe COVID-19-associated outcomes," the authors write.

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