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Centers for Disease Control and Prevention published data The level of protection provided by the Pfizer-BioNTech vaccine against Covid hospitalizations dropped significantly within four months of full vaccination, it said on Friday.
The data was released hours before a scientific advisory committee for the Food and Drug Administration recommended overwhelmingly against approval of a booster vaccine, the Pfizer-BioNTech vaccine for people 16 years and older. However, the debate over booster shots will continue as time passes and more data accumulates.
NS A new study found that the Pfizer vaccine was 91 percent effective in preventing hospitalizations from two weeks to four months after recipients received their second dose – a point normally considered to be fully vaccinated. Beyond 120 days, its effectiveness dropped to 77 percent.
The Moderna vaccine did not show comparable reductions in protection over the same time frame: It was 92 percent effective against hospitalizations four months after recipients were vaccinated, nearly the same as 93 percent efficacy before then.
The study said that not enough participants received the one-time Johnson & Johnson vaccine to compare its performance. Overall, the Johnson & Johnson vaccine was 71 percent effective in preventing hospitalizations.
The CDC study published Friday supported some suggesting that the Pfizer vaccine may provide less protection from hospitalization over time. But the available data are far from unanimous.
Other studies have shown that Pfizer’s efficacy against hospitalization remains above 90 percent, despite the spread of the Delta variant and the prolonged time since people had their second vaccination. Pfizer said that while Israel and the United States appear to define “severe disease” differently, data from Israel indicates a falling efficacy against serious illness.
The most recent CDC study was based on an analysis of nearly 3,700 adults hospitalized in the United States between March and August.
Individuals with compromised immune systems, who typically did not respond well to vaccines, were excluded from the study. However, vaccinated patients tended to be older people—the median age of the Pfizer cohort was 68—and it was unclear whether vaccine efficacy changed much in younger age groups. Previous studies have shown lower levels of protection in older people.
The study’s authors said the gap in the performance of the Moderna and Pfizer vaccines could be due to higher doses of mRNA in the Moderna vaccines or the four-week gap between Moderna vaccine doses. (The Pfizer vaccines were given three weeks apart.) They also said that other differences that were not noticed in the study participants who received both vaccines may also have affected the results.
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