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COVID-19 vaccine side effects: How common are they?

By Jill Granger

More than 170 million Americans have been fully vaccinated with the COVID-19 vaccine.

More than 170 million Americans have been fully vaccinated with the COVID-19 vaccine. 

COVID-19 cases are rising, and we’re bombarded daily with information affecting our vaccination decisions. One of the main reasons for hesitancy is concern about vaccine side effects. It’s a legitimate question. How can you wade through the information, decide what’s true and make an informed choice with confidence? Here are some steps to walk you through that process.

Identify your concerns and share them with a health care professional

It’s OK to wonder about vaccine safety and side effects. Talk to your doctor, who can provide trustworthy information and discuss potential side effects considering your medical situation. This can be reassuring and more valuable than drawing conclusions from social media posts, hearsay or videos, which may contain misinformation, misrepresent facts or make false claims. 

Get the facts from trusted sources

COVID-19 vaccines are part of the most intensive vaccine safety monitoring effort in U.S. history. COVID-19 vaccine safety information is collected daily through vaccine safety systems. These agencies monitor and quickly identify the small amount of unusual, adverse reactions that arise. This information is available to the public so we can make informed choices based on the latest data. 

The Food and Drug Administration (FDA) has determined that the current vaccine choices are safe and effective at preventing COVID-19 for most people, including severe illness and mortality. The FDA recently granted full approval for the Pfizer vaccine for people ages 16 or older. The Moderna and Johnson and Johnson vaccines remain under Emergency Use Authorization (EUA), as does the Pfizer vaccine for children ages 12 to 15. Still, the full approval process is moving forward. The main objective for the use of these vaccines is to prevent severe disease. Infections in fully vaccinated individuals, called “breakthrough infections,” are both expected and rare. Most people in this situation fully recover without complications.

See Finding Credible Vaccine Information | CDC.

What COVID-vaccine side effects have been reported so far?

When your defenses (immune system) are activated by the vaccine, you might experience some symptoms, but you won’t have an active infection. These symptoms include pain, redness or swelling at the injection site, headache, body aches, fatigue, fever, nausea or chills. They may be greater with the second shot and generally subside within a few days. Others report no symptoms at all.

Some very rare side effects have been reported and include:

Allergic Reactions: A small number of rare severe allergic reactions (anaphylaxis) have been reported to all three vaccines. For this reason, people are asked to stay briefly following vaccination. Those with a history of severe, immediate allergic reactions or injectables should talk to their doctor before receiving a COVID-19 vaccine. Severe reactions are treated with epinephrine (EpiPen®), or hospitalization, and can be life-threatening if untreated. However, there have been no reported deaths from allergic reactions to these vaccines.

For more information, see COVID-19 Vaccines for People with Allergies | CDC.

Myocarditis and Pericarditis: Myocarditis is inflammation of the heart muscle. Pericarditis is inflammation of the pericardium, a lining that forms a sac around the heart. These inflammations were reported in a small number of young male patients (16-24 years old), especially after the second dose of mRNA vaccines (Pfizer-BioNTech, Moderna). Symptoms include chest pain, shortness of breath, a heartbeat that is fast, fluttering or pounding.

Most patients fully recover if treated immediately, but this can be life-threatening if untreated. If you get a COVID-19 infection, the risk of getting these side effects would be greater than from the vaccine.

For more information, see Myocarditis and Pericarditis Following mRNA COVID-19 Vaccination | CDC.

Thrombosis (blood clots) with Thrombocytopenia syndrome (TTS): During thrombosis, blood clots form and block the blood vessels. In thrombocytopenia, there are low numbers of platelets cells that help blood clot. This can cause internal bleeding. These issues were reported in a small number of cases after more than 12 million doses (Johnson & Johnson and Moderna COVID-19 vaccines).

These conditions can be life-threatening if untreated. Most cases have occurred one to two weeks after vaccination in women, ages 18 to 49. If you get a COVID-19 infection, the risk of thrombosis is greater than you would get from the vaccine.

Read more about TTS and the Johnson & Johnson COVID-19 vaccine.

Guillain-Barré Syndrome: This syndrome is a rare side effect where the immune system attacks nerve cells. It occurs mostly in men older than 50 and can cause muscle weakness or paralysis. Most patients recover, but some experience permanent nerve damage or death.

For more information, see GBS (Guillain-Barré Syndrome) and Vaccines | Vaccine Safety | CDC.

Share your concerns, get the facts from sources you trust, and evaluate your personal situation. These steps can go a long way to be confident in your decision.


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