Why some vaccinated people still get hospitalized with COVID-19
It's relatively rare to be hospitalized after getting vaccinated against COVID-19, but those who do typically have significant health issues that contribute to their risk.
Infectious disease physicians at Allegheny Health Network wanted to better understand who's at risk of being hospitalized even after vaccination, so they reviewed cases of COVID-19 patients at AHN hospitals during summer 2021 and published the findings this month in the journal Open Forum Infectious Diseases.
"We know that vaccination really reduces your risk of hospitalization and death, but it doesn't completely eliminate it," said Dr. Matthew Moffa, medical director of infection prevention at AHN West Penn Hospital and one of the authors of the study.
Across eight AHN hospitals in Western Pennsylvania during the time period studied, 473 patients were hospitalized with COVID-19. Of those, 128 were fully vaccinated at the time. The other 345 were either unvaccinated or didn't get a full vaccine course.
Among the fully vaccinated patients, 73% had symptoms of COVID-19 while the other 27% were considered incidental cases—that is, they were admitted to the hospital for other reasons but tested positive for COVID-19 in the hospital.
The patients hospitalized for COVID-19 symptoms had an average age of 73 and most had other health problems, such as diabetes, high blood pressure, chronic kidney disease or chronic lung disease. About half were overweight and a quarter were severely immunocompromised, meaning they were on chemotherapy for cancer, had a prior organ transplant or stem cell transplant, or they were on medications to suppress their immune system.
For many immunocompromised patients, the vaccines don't generate enough antibodies to protect against COVID-19. A new preventive treatment, Evusheld, has been authorized for these individuals. The treatment wasn't available at the time of the study.
Of the 93 fully vaccinated patients, 14 needed to be placed on mechanical ventilation and 19 died in the hospital of COVID-19.
As of Jan. 18, the Pennsylvania Department of Health reported that 85% of hospitalizations with COVID-19 as the primary diagnosis or cause of admission were in unvaccinated or not fully vaccinated people.
"For those we identified at risk for hospitalization after vaccination, we strongly encourage that you get boosted if not already boosted," Dr. Moffa said. During the study period, booster shots were not yet available.
If high-risk patients do get sick with COVID-19, he encouraged seeking out early outpatient treatments, such as monoclonal antibodies and new antiviral pills, to help prevent hospitalization.
Dr. Moffa said there were likely more incidental COVID-19 hospitalizations during the omicron wave than during the study period, when delta was surging last summer.
He said the major takeaway from the study is that vaccines are very effective against hospitalization and death, but some people are still at risk despite being fully vaccinated.
"Everyone wants to move on from the pandemic, but we still have a lot of vulnerable people out there that have done the right thing and gotten vaccinated," Dr. Moffa said. "That's why it's important for everyone to try to cocoon them by more vaccination, driving down case rates to reduce their risk of having a bad outcome."
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