Study finds who may get more severe illness from a COVID-19 breakthrough case – SFGate

Vaccinated people who are infected with COVID-19 and get a so-called breakthrough case that leads to severe illness are more likely to be older and have preexisting health conditions, a new study found.

"Overall, older population with underlying heart or lung disease, or with weakened immune system were the most highly represented in those with breakthrough cases with symptoms," Dr. Hyung Chun of the Yale School of Medicine, who led the study, wrote in an email.

Chun and his Yale colleagues identified 969 patient who were admitted to hospitals in the Yale New Haven Health System and who tested positive for COVID across a 14-day period from March 23 to July 1, according to commentary posted on the Lancet Infectious Disease website on Sept. 7.All patients were required to get tested when they were admitted and may have come to the hospital for illness other than COVID.

Roughly 18% of the patients who tested positive received at least one vaccine dose and a third of these were fully vaccinated, records showed.

The team focused on those fully vaccinated people and found a quarter of them (14 people) had severe or critical disease and required supplementary oxygen support. Four were in the intensive care unit, one on a mechanical ventilator and three died.

The patients with severe disease ranged in age from 65 to 95 years old and had a median age of 80.5, the researchers said. They had preexisting comorbidities including cardiovascular disease, lung disease, obesity and Type 2 diabetes. Some patients were on immunosuppressive drugs that may impact vaccine efficacy.

A large body of research shows COVID-19 vaccines are effective and have been instrumental in curbing the pandemic, but in rare cases people who are fully vaccinated contract the virus and get what are called breakthrough cases. In even rarer cases, a breakthrough case results in severe illness.The Centers for Disease Control and Prevention has received reports of 14,115 patients with COVID-19 vaccine breakthrough infection who were hospitalized or died. This accounts for an extremely small percentage of the 178 million fully vaccinated individuals in the United States.

"Vaccines continue to remain highly effective in preventing severe illness due to COVID-19," Chun wrote. "The likelihood of developing severe COVID-19 infection remains far lower for those vaccinated compared to those unvaccinated. Emerging data on breakthrough cases will need to be closely followed to determine the most effective strategies for booster vaccines."

The study was done before the highly transmissible delta variant became the predominant COVID variant in the United States. Chun said more research is needed to determine the impact of the delta variant on breakthrough cases.

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Study finds who may get more severe illness from a COVID-19 breakthrough case - SFGate