Stamford Advocate

Yale studies COVID breakthrou­gh cases

- By Newsroom Staff

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


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


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.

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