Vaccine effectiveness against hospitalization falls for oldest patients

The effectiveness of the COVID-19 vaccines against hospitalization appears to drop over time among adults over 75, although it still remained above 80% at the end of July, according to an analysis released by the Centers for Disease Control and Prevention.

The agency's finding is the latest to suggest protection against severe disease may be starting to wane among the most vulnerable Americans vaccinated earliest in the pandemic, as the country battles a record wave of infections fueled by the Delta variant. But the agency also conceded that drawing conclusions about the amount of time vaccines protect older or more vulnerable people from hospitalization would not be easy.

"It actually may be very difficult for us to disentangle time, since vaccination and the impact of the Delta variant, especially in some populations that we know were vaccinated earlier in the time course. So if we see waning in the last couple of months, it could be really difficult," Dr. Sara Oliver, a key CDC vaccine official, told the panel. The effectiveness at preventing hospitalization "remains high, 94% or higher, for adults 18 to 49," Dr. Oliver said.

16.1% of hospitalized patients were fully vaccinated in June. Hospitalizations among people who were fully vaccinated were more likely to have occurred among older residents of nursing homes, and among those with underlying conditions — nearly a third with immunosuppressive conditions. While top federal health officials previously said they were planning for the possibility that third doses of the Pfizer and Moderna vaccines would be needed eight months after Americans received their first two shots, recent data from the drugmakers and abroad have suggested booster shots might be needed sooner than six months from vaccination. The panel's members voted unanimously to recommend the continued use of the shots to prevent COVID-19, finding that the vaccines' benefits in averting COVID-19 hospitalization and death outweighed the risks of rare but serious side effects like myocarditis and pericarditis. Only 701 reports from the rare heart inflammation cases have been received by the CDC of confirmed hospitalizations in people under 30 following their vaccination. Most have since been discharged and recovered from their symptoms.

"The risks that we're talking about following vaccination is generally within seven days but the benefits last for far longer than seven days," Dr. Grace Lee, a pediatrics professor at Stanford University and chair of the advisory committee.

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