The median age of fully vaccinated people who developed a severe breakthrough COVID-19 infection from March through June was 80, a study published Sept. 7 in The Lancet Infectious Diseases found.
The research was based on an analysis of 969 COVID-19 patients who were admitted to Yale New Haven (Conn.) Health between March 23 and July 1, 2021. Of those, 103 had received at least one dose of a COVID-19 vaccine, and 54 were considered fully vaccinated.
Researchers considered the 54 fully vaccinated people who contracted COVID-19 as breakthrough cases, meaning they began experiencing symptoms or received a positive test at least 14 days after their final dose. Twenty-five (46 percent) of these patients were admitted to the hospital for reasons unrelated to COVID-19 and received an incidental positive test, meaning they were asymptomatic.
A total of 14 breakthrough patients (26 percent) had severe or critical illness. The median age of these patients was 80.5 years. Most of these patients had heart disease, seven had lung disease, and seven had diabetes. All 14 of the patients with severe or critical illness were on ventilators, four were admitted to the intensive care unit and three died, researchers said.
"Identifying who is more likely to develop severe COVID-19 illness after vaccination will be critical to ongoing efforts to mitigate the impact of these breakthrough infections," said Hyung Chun, MD, associate professor of cardiology at Yale School of Medicine. "These cases are extremely rare, but they are becoming more frequent as variants emerge and more time passes since patients are vaccinated."