CDC assessment finds mRNA COVID-19 vaccines reduce COVID-19-related hospitalizations by 94%

April 29, 2021

Both mRNA COVID-19 vaccines (Pfizer-BioNTech and Moderna) authorized and recommended in the United States protect against COVID-19-related hospitalization among adults 65 years and older, according to a new Centers for Disease Control and Prevention (CDC) assessment that finds fully vaccinated adults 65 years and older were 94% less likely to be hospitalized with COVID-19 than people of the same age who were not vaccinated.

People 65 and older who were partially vaccinated were 64% less likely to be hospitalized with COVID-19 than people who were not vaccinated. People were considered “partially vaccinated” two weeks after their first dose of mRNA vaccine and “fully vaccinated” two weeks after their second dose.

These are the first real-world findings in the U.S. confirming clinical trial data showing mRNA vaccines prevent severe COVID-19 illness. The findings provide additional support for CDC’s recommendation for COVID-19 vaccination among people 65 and older in the U.S. population under the Emergency Use Authorization (EUA) for the applicable COVID-19 vaccine as the risk for severe illness with COVID-19 increases with age, with older adults at highest risk.

The assessment looked at hospitalizations in two U.S. hospital networks covering 24 hospitals in 14 states. Vaccine effectiveness was assessed by comparing the odds of COVID-19 vaccination among hospitalized people who tested positive for the virus that causes COVID-19 (these were case-patients) versus those who tested negative (these were controls). Among 417 participants in the assessment, there were 187 case-patients and 230 controls. Close to half of the patients were more than 75 years old.

While early reports from Israel also documented the real-world effectiveness of COVID-19 vaccination, including among older adults, those reports only looked at vaccination with Pfizer-BioNTech vaccine. In this CDC assessment, both Pfizer-BioNTech and Moderna vaccine products were equally represented.

As expected, the assessment confirmed that vaccination provided no protection to people who had received their first dose fewer than two weeks earlier. It takes two weeks for the body to form an immune response after vaccination.

Two networks previously established to conduct surveillance for serious influenza disease provided the data for this assessment: Hospitalized Adult Influenza Vaccine Effectiveness Network (HAIVEN) and Influenza Vaccine Effectiveness in the Critically Ill (IVY).

This assessment is one of many planned COVID-19 vaccine effectiveness assessments to evaluate the real-world benefits of COVID-19 vaccines. Results from these assessments will help inform vaccine policy decisions aimed at saving lives and decreasing serious COVID-19 disease as much as possible.

CDC recommends everyone 16 years of age and older in the U.S. population under the EUA get the applicable COVID-19 vaccine as soon as possible. 

CDC has the release

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