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Breakthrough COVID-19 hospitalizations of fully vaccinated individuals most often affect older adults and those with chronic health conditions, according to a new analysis of hospital data by the Kaiser Family Foundation and Epic Research.
As of Sept. 30, 56% of the entire population, 67% of all adults and 83% of older adults (those aged 65 or more years) were fully vaccinated against COVID-19. Those unvaccinated (44%) make up a smaller share of the U.S. population but the vast majority (85%) of COVID-19 hospitalizations.
According to data on more than 120,000 COVID-19 hospitalizations from June through September, 69% of breakthrough COVID-19 hospitalizations occurred among fully vaccinated older adults compared with 21% among people aged 50 to 64 and 10% among people younger than 50.
Comparatively, COVID-19 hospitalizations among those who were not fully vaccinated were more likely among people aged 50 to 64 (30%) and those under 50 (41%). People 65 and older represented three in 10 hospitalizations of those unvaccinated (29%).
The analysis also showed that larger shares of fully vaccinated adults hospitalized with breakthrough COVID-19 had certain chronic conditions, including hypertension, diabetes, heart failure or chronic obstructive pulmonary disease, compared with unvaccinated hospitalizations.
Researchers surmised that older adults with chronic conditions are more likely to have weakened immune systems and, as a result, COVID vaccines may provide less protection. They also noted that older adults were among the first to receive coronavirus vaccines and may have experienced declining immunity over time.
Fully vaccinated people with breakthrough infections experienced shorter hospital stays compared with other groups who were not fully vaccinated. Among patients aged 65 and older, the median COVID hospital stay was 1.1 days shorter for those fully vaccinated (5.6 days) than for those not fully vaccinated (6.7 days).
The researchers also found that fully vaccinated individuals hospitalized with breakthrough infections were less likely than their unvaccinated counterparts to have COVID-related complications, such as viral pneumonia or respiratory failure. They also were less likely to require a ventilator or dexamethasone treatment.
“This suggests that fully vaccinated patients with COVID-19 diagnoses may be somewhat more likely to be in the hospital primarily for reasons other than COVID-19,” the authors stated.
Despite the widespread availability of vaccines against it, COVID-19 was the second- leading cause of death in the United States overall in September.
“Although people not fully vaccinated continue to represent the vast majority of COVID-19 hospitalizations, understanding the characteristics of people with breakthrough hospitalizations can help inform ongoing policy making around the pandemic respondents and can also inform individuals about their potential risks,” the authors wrote.
