Characteristics of Vaccinated Patients Hospitalized with COVID-19 Breakthrough Infections

While people who are fully vaccinated against COVID-19 have a significantly reduced risk of severe illness, some hospitalizations and deaths have been reported among fully vaccinated people with breakthrough COVID-19 infections.

This brief describes the characteristics of fully vaccinated hospitalized patients who have COVID-19 breakthrough infections, in comparison to people who are not fully vaccinated and hospitalized with COVID-19. Compared to those who are unvaccinated, a small share (15%) of hospital admissions for COVID-19 between June and September involve people who were fully vaccinated against the disease.

It finds that age is highly correlated with breakthrough hospitalizations, and a greater share of people hospitalized with a breakthrough COVID-19 infection had a comorbidity than people hospitalized with COVID-19 who were not fully vaccinated. It also finds that fewer breakthrough COVID-19 hospitalizations included COVID-related respiratory complications or treatments, suggesting fully vaccinated patients hospitalized with breakthrough COVID-19 may have been more likely to be hospitalized for unrelated reasons.

The analysis examines data from the four-month period from Epic’s Cosmos research platform, which includes data for more than 120,000 hospitalizations with a COVID diagnosis during the four-month period. Patients are considered “fully vaccinated” if they received a dose of Johnson & Johnson vaccine or two doses of the Pfizer or Moderna vaccine at least two weeks before they were hospitalized, regardless of whether they were eligible for or received a booster shot.

The analysis is available on the Peterson-KFF Health System Tracker, an online information hub dedicated to monitoring and assessing the performance of the U.S. health system.