mRNA COVID-19 Vaccine Less Protective in Elderly With Comorbidity

At ≥7 days after second dose, effectiveness of mRNA COVID-19 vaccine was 69 percent against infection, 86 percent against related death

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THURSDAY, Dec. 23, 2021 (HealthDay News) -- Among elderly veterans with a high burden of comorbidity, messenger RNA (mRNA) COVID-19 vaccination is 69 percent effective against severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection and 86 percent effective against SARS-CoV-2-related death, according to a study published online Dec. 21 in the Annals of Internal Medicine.

George N. Ioannou, B.M.B.Ch., from the University of Washington in Seattle, and colleagues examined the effectiveness of mRNA COVID-19 vaccines among 5,766,638 U.S. persons receiving care in the Veterans Affairs health care system. A total of 2,099,871 who received at least one dose of the Moderna or Pfizer-BioNTech COVID-19 vaccine from Dec. 11, 2020, to March 25, 2021, were matched to unvaccinated controls in a 1:1 ratio.

The groups were well matched; individuals were predominantly male and had advanced age (mean, 68.7 years), diverse racial and ethnic distribution, and considerable comorbidity burden. The researchers found that at seven or more days after the second dose, vaccine effectiveness was 69 percent against SARS-CoV-2 infection and 86 percent against SARS-CoV-2-related death. There was a decrease in vaccine effectiveness with increasing age and comorbidity burden.

"In an elderly population of U.S. veterans with high comorbidity burden, COVID-19 vaccine effectiveness against infection was substantially lower than previously reported but effectiveness against death was very high," the authors write.

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