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Real-World Results Confirm Vaccine Effectiveness in Older Adults

A man in a mask and a University of Pittsburgh Emergency Medicine uniform delivers vaccine to man in foreground
A multisite study for the Centers for Disease Control and Prevention (CDC) confirms that the Pfizer-BioNTech and Moderna vaccines being distributed to fight COVID-19 are highly effective in preventing hospitalizations among older adults, the most at-risk group for serious complications from the disease. 

Clinicians and researchers from the University of Pittsburgh’s School of Medicine and Graduate School of Public Health helped determine the results of the CDC led study. Patients were enrolled from 24 medical centers in 14 states.

Fully vaccinated adults 65 and older are 94% less likely to be hospitalized with COVID-19 than people of the same age who have not received both shots, according to the CDC study, which was published last week. This marks the first real-world evidence—data obtained outside of the context of randomized controlled trials and produced during clinical practice—in the United States that both vaccines prevent severe COVID-19-related illness.

Richard Zimmerman, a professor in the University’s Departments of Family Medicine and Clinical Epidemiology who helped lead Pitt’s effort in the CDC study, said the findings confirm the clinical trial data for the mRNA vaccines from Pfizer-BioNTech and Moderna.

“It gives us confidence that the clinical trial results are good, and it gives us confidence in this vaccine,” said Zimmerman, an influenza expert.

The study also showed that people who were partially vaccinated—meaning two weeks after their first dose of mRNA vaccine—were 64% less likely to be hospitalized with the disease than the unvaccinated.

Along with Pitt’s Fernanda P. Silveira, director of clinical operations for transplant infectious diseases, and Donald B. Middleton, vice president of Family Medicine at UPMC St. Margaret, Zimmerman leads a team that was previously established to conduct surveillance for serious influenza disease as part of the Hospitalized Adult Influenza Vaccine Effectiveness Network (HAIVEN). 

“It’s hard to knock 94% effectiveness in older adults,” Zimmerman said. “That’s pretty good, far better than any flu vaccine.”