How Effective Are mRNA COVID-19 Vaccines?

COVID-19 mRNA vaccines reduce infection risk by 91 percent, CDC says

(RxWiki News) Wondering how effective your Moderna or Pfizer COVID-19 vaccine really is? The Centers for Disease Control and Prevention (CDC) has an answer.

According to a new study from the CDC, mRNA vaccines reduce the risk of COVID-19 infection by 91 percent for fully vaccinated people.

And for those few vaccinated people who do get COVID-19, the illness is shorter and milder, the agency said.

This research adds to the already large body of evidence that shows that vaccination against COVID-19 is an effective way to prevent illness, the CDC noted.

“COVID-19 vaccines are a critical tool in overcoming this pandemic,” said CDC Director Dr. Rochelle P. Walensky in a press release. “Findings from the extended timeframe of this study add to accumulating evidence that mRNA COVID-19 vaccines are effective and should prevent most infections — but that fully vaccinated people who still get COVID-19 are likely to have milder, shorter illness and appear to be less likely to spread the virus to others. These benefits are another important reason to get vaccinated.”

This COVID-19 vaccine study looked at nearly 4,000 health care workers, essential workers and first responders over 17 weeks. Participants were tested for COVID-19 once a week.

Those who were fully vaccinated were 91 percent less likely than unvaccinated participants to get COVID-19. Those who were partially vaccinated with only one dose of the two-dose series or within two weeks of the second dose were 81 percent less likely to test positive for COVID-19.

Compared to unvaccinated people who became sick, the few vaccinated participants who did get COVID-19 spent on average six fewer days sick and two fewer days sick in bed, according to the CDC. They were also around 60 percent less likely to develop symptoms of COVID-19.

Other findings from this study suggest that vaccinated people who become infected with COVID-19 are less likely to spread the virus to others. This is likely because they appeared to have a smaller amount of the virus detectable in their systems.

This research looked at the two-dose mRNA vaccines from Pfizer and Moderna. It did not examine the one-dose vaccine from Johnson and Johnson.

Health officials recommend COVID-19 vaccination for everyone who is at least 12 years old. If you have any questions or concerns, speak with your health care provider.

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Review Date: 
June 16, 2021