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mRNA vaccines perform well in the real world

Two masked healthcare workers walking outside.

April 6, 2021—Researchers have been working with messenger RNA (mRNA) vaccines for decades. But before 2020, most of us had never heard of them. Then two new mRNA vaccines—from Moderna and Pfizer—were the first in the U.S. to be OK'd for use against COVID-19.

Clinical trials found these vaccines to be very effective. But you might have wondered: Will mRNA vaccines work well in the real world too? Now we can see the answer is yes. That's partly thanks to a new study of front-line workers from the Centers for Disease Control and Prevention.

Solid protection

The study looked at nearly 4,000 healthcare workers, first responders and other essential workers who received either the Pfizer or the Moderna mRNA vaccine.

For about three months, these workers had tests once a week for SARS-CoV-2, the virus that causes COVID-19.

Among the key findings:

Fully vaccinated people were 90% less likely to have the virus. You are fully vaccinated about two weeks after your second dose of a two-dose vaccine. That is how long it takes for the body to build up immunity.

Partially vaccinated people were 80% less likely to have the virus. Even those who had not yet had their second dose gained a good degree of protection. You are partially vaccinated two weeks after your first dose.

The vaccines reduced the risk of all SARS-CoV-2 infections, not just those that caused symptoms. That's good news because even people who don't feel sick can spread the virus to others.

More studies are likely to come. But this reassuring first wave of data suggests that mRNA vaccines are reliable in the real world.

Curious to know more about mRNA vaccines? Learn how COVID-19 vaccines work.

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