This Is How Effective Moderna and Pfizer Really Are, New CDC Study Says

The study looked at how well the COVID vaccines work in real-life scenarios.

The Moderna and Pfizer vaccines have already been proven safe and highly effective in clinical trials. Until recently, however, there hadn't been any studies on how the COVID shots work in real-world conditions. Now, the Centers for Disease Control and Prevention (CDC) has published a report that shows just how effective the Moderna and Pfizer vaccines really are. Keep reading to find out how much these shots can protect you, and for reactions to look out for, If 1 of These 3 Body Parts Starts Swelling Up After Your Vaccine, Call a Doctor.

The Moderna and Pfizer vaccines are both highly effective in real-world conditions.

Shot of a doctor applying a band aid after injecting a patient in his arm with COVID vaccine
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The March 29 study from the CDC concluded that the Moderna and Pfizer vaccines are both highly effective at preventing both symptomatic and asymptomatic COVID infections under real-world conditions. To get this data, the CDC tracked the COVID tests of 3,950 health care workers, first responders, and other essential and frontline workers for 13 weeks. These people were at high risk of being exposed to the virus by virtue of their jobs, but were infected at very low rates. The study found that under these conditions, the shots were 90 percent effective against COVID infections in fully vaccinated individuals and 80 percent effective in those with partial immunization. And for more on vaccine side effects, discover The One Side Effect That's Much More Common With Pfizer, Data Shows.

The study also concluded that COVID transmission is unlikely after vaccination.

friends enjoy shopping and snacks at downtown Neon District of Norfolk, Virginia (selective focus)
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A common concern among people who have received the vaccine before their loved ones is whether or not they can still carry and transmit the virus. The study suggests that transmission after vaccination is unlikely, since infections—even asymptomatic ones—were rare. "This is important because preventing both asymptomatic and pre-symptomatic infections among health care workers and other essential workers through vaccination can help prevent the spread of SARS-CoV-2 to those they care for or serve," the CDC said in a statement. And for more essential vaccine guidance, learn The Only Medication You Should Take Before Your COVID Vaccine, Experts Say.

Variants of the virus may not impact the efficacy of the vaccines.

A young man wearing a face mask and a backpack stands on a city street.
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Health experts have expressed concern that different variants of the virus could render the vaccines less effective. However, the study suggests that the strains may not be an issue. The New York Times pointed out "troubling variants were circulating during the time of the study—from December 14, 2020 to March 13, 2021—yet the vaccines still provided powerful protection." And for more up-to-date COVID news delivered straight to your inbox, sign up for our daily newsletter.

There is promising evidence that the vaccination effort is working.

Woman getting COVID vaccine
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"This study shows that our national vaccination efforts are working," CDC director Rochelle Walensky, MD, said in the statement. "These findings should offer hope to the millions of Americans receiving COVID-19 vaccines each day and to those who will have the opportunity to roll up their sleeves and get vaccinated in the weeks ahead. The authorized vaccines are the key tool that will help bring an end to this devastating pandemic." The CDC notes that this is only the first of many studies on the efficacy of the COVID vaccines. And for more vaccine advice, find out The Best COVID Vaccine to Get If You're Hesitant About Vaccinations, Doctors Say.

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