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This COVID Vaccine Has the Most Side Effects, Study Says

But that doesn't mean you should avoid it. Here's why.

One of the three currently approved COVID-19 vaccines seems to produce more side effects, an early study has found. According to research published this week in JAMA, "To facilitate rapid assessment of COVID-19 vaccines, in 2020, the Centers for Disease Control and Prevention (CDC) established v-safe, a new active surveillance system for collecting near–real-time data from COVID-19 vaccine recipients in the US." That data showed respondents had more side effects from one vaccine in particular. Read on to find out which one—and remember that these side effects are perfectly normal and should not prevent you from getting vaccinated—and to ensure your health and the health of others, don't miss these Signs Your Illness is Actually Coronavirus in Disguise.


The Moderna Vaccine Had More Side Effects, Say Respondents


According to the research, people who get the Moderna vaccine say they've experienced more side effects than people who get the shots developed by Pfizer/BioNTech.

The results were based on V-Safe, a text-message-based program by the Centers for Disease Control and Prevention that's designed to track side effects in vaccine recipients. For the first week after each vaccine dose, people who enroll are prompted to fill out a daily survey about their symptoms. See the next slide for what the side effects were.


Side Effects Included an Injection-Site Reaction and Fatigue

Woman sleeping on the couch in the living room.

Among the 3.6 million people who got their first dose of a COVID-19 vaccine before Feb. 21—and also enrolled in V-Safe and checked in at least once—about 70 percent reported an injection-site reaction, such as pain or swelling. About half had a full-body reaction like fatigue or chills. 

People who got a Moderna shot were more likely to have a side effect, compared to those who got the Pfizer formulation: 73 percent reported an injection-site reaction, compared with 65 percent of people who had a Pfizer dose. Nearly 51 percent of Moderna vaccine recipients had full-body symptoms, compared with 48 percent of people who got the Pfizer shot.


More People Had Side Effects After the Moderna Second Shot in Particular

Senior woman with arm pain

The side-effect gap widened with the second shot. About 82 percent of people getting their second Moderna shot reported injection-site pain, compared to less than 69 percent who got the Pfizer shot. Overall, 74 percent of people said they experienced side effects after their Moderna shot, versus 64 percent of people who had the Pfizer vaccine.

RELATED: Doctors Say "DO NOT" Do This After Your COVID Vaccine


There Have Been Some Reported Cases of "Moderna Arm"


Moderna shots have been more often associated with a side effect nicknamed "COVID arm" — or "Moderna arm" — in which vaccine recipients have developed a rash about a week or more after injection.

According to research published this week in the Journal of the American Academy of Dermatology, these delayed skin responses—which can occur from one to eight days after injection—are not dangerous and don't preclude recipients from receiving a safe second injection. 

"COVID arm" or "Moderna arm" are different than a severe allergic reaction to the vaccine, such as anaphylaxis, a potentially life-threatening swelling of the airway. That usually happens within minutes of the injection, which is why the CDC has advised everyone to wait 15 to 30 minutes after getting the vaccine before leaving the injection site.

But rashes that start later don't signify a serious problem. "For people whose rashes started four or more hours after getting the vaccine, zero percent of them went on to get anaphylaxis or any other serious reaction," said Dr. Esther Freeman, director of global health dermatology at Massachusetts General Hospital, in USA Today. "Zero is a nice number."

She added: "People can feel reassured about getting the second dose of their vaccine."


Why Does This Happen?

African American man in antiviral mask gesturing thumb up during coronavirus vaccination, approving of covid-19 immunization

Experts say that side effects related to the COVID vaccine are a good sign — that your immune system is "booting up" to fight an invading virus. As for why one formulation is more associated with side effects than another, it's unclear. As for yourself, get through this pandemic at your healthiest, don't miss these 35 Places You're Most Likely to Catch COVID.

Michael Martin
Michael Martin is a New York City-based writer and editor. Read more about Michael
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