The COVID-19 vaccines from Pfizer and Moderna are 94% effective at preventing hospitalization among fully vaccinated older Americans, according to real-world data released by the U.S. Centers for Disease Control and Prevention.
The vaccines also are 64% effective among adults ages 65 and older who had received only the first dose, the findings show.
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These latest data confirm findings from the clinical trials conducted prior to the shots receiving emergency authorizations from the U.S. Food and Drug Administration. Those studies found the vaccines' overall effectivenesses to be about 94% to 95%.
CDC Director Rochelle P. Walensky said the findings are "welcome news" for the two-thirds of seniors who already are fully vaccinated.
"COVID-19 vaccines are highly effective and these real-world findings confirm the benefits seen in clinical trials, preventing hospitalizations among those most vulnerable," Walensky said. "The results are promising for our communities and hospitals. As our vaccination efforts continue to expand, COVID-19 patients will not overwhelm health care systems – leaving hospital staff, beds and services available for people who need them for other medical conditions."
The study also confirmed that the vaccines do not offer partial protection until two weeks after the first dose, nor full protection until two weeks after the second dose, researchers said.
The analysis included data from 24 hospitals in 14 states, including Pennsylvania, though researchers said more states need to be included to determine whether the findings represent the entire U.S. population.
The study included 417 seniors who had been hospitalized with COVID-19-like symptoms between Jan. 1 and March 26. About 187 of the patients actually tested positive for the coronavirus.
Among the patients who tested positive, only one person had been fully vaccinated with either the Pfizer or Moderna vaccines and 18 had been partially vaccinated.
The researchers found higher vaccination rates among the 230 adults who tested negative for the coronavirus. Forty-four of them were partially vaccinated and 18 were fully vaccinated.
An earlier CDC study examined the real-world effectiveness of the Pfizer and Moderna vaccines at preventing infection among front-line workers. The two-dose vaccines reduced infection risk by 90% in a study of 3,950 health care personnel, first responders and other essential employees.
The CDC recommends everyone 16 years of age and older receive one of the authorized COVID-19 vaccines as soon as possible.