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September 29, 2021

COVID-19 boosters are just as safe as the first two shots, CDC study shows

The side effects are similar to those felt after the second dose

Prevention COVID-19
COVID-19 vaccine booster shots Mat Napo/Unsplash

COVID-19 booster shots have a safety profile similar to that produced by the second vaccine dose, a new CDC study shows. The most common side effects are pain at the injection site, fatigue and headaches.

The most common side effects of COVID-19 booster shots are similar to those experienced after the second dose – pain at the injection site, fatigue and headaches, according to data released Tuesday by the U.S. Centers for Disease Control and Prevention. 

Overall, the side effects are mostly mild, the CDC study shows. Recipients start to feel the side effects the day after the injection. 

Almost 2.8 million people have received a booster shot since the U.S. Food and Drug Administration authorized additional doses of the Pfizer-BioNTech and Moderna vaccines for people with compromised immune systems in August. 

That number will grow significantly now that the CDC also has recommended a booster shot for people who received the Pfizer vaccine and are ages 65 or older, long-term care residents or at higher risk of COVID-19 due to underlying health issues or their occupations. 

The CDC-led study looked at data from 22,191 people who received a booster shot and responded to questions on the CDC's smartphone app, v-safe. Almost all of them received the same booster shot as their initial doses.

Arm pain was slightly more common after the third shot, but headache or fatigue were a little less common, the researchers reported. About 28% said they were unable to conduct their normal daily activities because of the side effects. 

"We are very comfortable with the safety of these vaccines. They've been given to millions and millions and millions and millions of people," Dr. Helen Keipp Talbot, a member of the CDC's Advisory Committee on Immunization Practices, told NBC News.

"But that doesn't mean we're going to stop monitoring and stop looking" for adverse events, she added. "We're always going to be cautious and careful."

The Philadelphia Department of Public Health began administering booster doses of the Pfizer vaccine Saturday to eligible people. Existing COVID-19 vaccine providers are administering Pfizer's booster shot. Residents can find the nearest vaccine clinic by calling (215) 685-5488 or by visiting the city's website

In August, the Biden administration announced its intentions to offer booster shots as the highly-contagious delta variant surged across the country and COVID-19 cases among vaccinated people increased. 

Though the vaccines still remain highly effective at preventing severe disease, hospitalization and death, previous CDC studies show COVID-19 cases have been more common among vaccinated people since the delta variant arrived. 

Some scientists have argued that most people don't need COVID-19 booster shots due to their effectiveness at preventing severe illness. The World Health Organization has urged countries against offering booster shots, emphasizing a greater need for vaccines in areas with limited access.

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