Yale studies COVID breakthrough cases

NEW HAVEN — Breakthrough cases of COVID-19 are relatively rare, but a new study by Yale University researchers found some vaccinated patients who were hospitalized with a second infection suffered from severe illness and even death.

The study, led by Dr. Hyung Chun, associate professor of medicine at the Yale School of Medicine, found 54 fully vaccinated COVID patients hospitalized with breakthrough cases. Of those, 14 were seriously ill: All needed oxygen support, four were admitted to the intensive care unit and three died, according to a release.

“It was certainly a finding that we weren’t expecting, that such a rather large percentage of patients who were fully vaccinated and hospitalized would be severely ill with COVID,” Chun said

Tuesday.

The 14 patients who were seriously or critically ill were older — between 65 and 95 years old, with a median age of 80.5 — and had preexisting comorbidities, such as cardiovascular disease and Type 2 diabetes, the release said. Some also were on immunosuppressive drugs that may affect vaccine efficacy.

“There are risk factors that would put you at a higher risk of more severe illness due to the breakthrough infection,” Chun said. The much lower risk of younger, healthy vaccinated people falling seriously ill from a breakthrough case “has certainly been shown by multiple other studies,” he said.

The 54 vaccinated patients were among 969 hospitalized people studied who tested positive for COVID between March and July 2021, 5.6 percent of the COVID-positive patients. The study was published Tuesday in Lancet Infectious

Diseases.

Chun said the 54 breakthrough cases were not all hospitalized because of COVID, but all admitted patients are given a COVID test. “Some of those were likely to be incidental positive PCR tests,” he said.

“These cases are extremely rare, but they are becoming more frequent as variants emerge and more time passes since patients are vaccinated,” Chun said in the release. “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.”

As of Aug. 30, 12,908 patients with breakthrough COVID had been hospitalized or died, according to the Centers for Disease Control and Prevention, which is less than 0.008 percent of fully vaccinated individuals in the United States.