COVID Vaccine Side Effects

Featured Experts:

  • Dr. Maragakis

  • Dr. Gabor Kelen

Published on November 9, 2021

It's helpful to understand side effects before you get a COVID-19 vaccine. For the vast majority of people already vaccinated in the U.S. for COVID-19, the side effects, if any, have been mild. Serious or persistent side effects associated with the approved or authorized vaccines are extremely rare.

Lisa Maragakis, M.D., M.P.H., senior director of infection prevention, and Gabor Kelen, M.D., director of the Johns Hopkins Office of Critical Event Preparedness and Response, help you understand side effects associated with the COVID-19 vaccines.

Common Side Effects of COVID Vaccines

After getting vaccinated for COVID-19, you might experience some temporary symptoms similar to those you might notice when you get a flu shot, such as a sore, swollen arm where you got the shot. You might run a fever and experience body aches, headaches and tiredness for a day or two. Chills and swollen lymph nodes can also occur.

These symptoms do not mean you are sick. They signal that your immune system is responding to the shot and building up protection against the coronavirus.

For the 2-dose vaccines, are side effects different from the first to second shot?

Both the Pfizer and the Moderna COVID-19 vaccinations involve two injections separated by several weeks. For these two-shot vaccinations:

  • If you had COVID-19 before being vaccinated, the first injection may cause more noticeable side effects than for people who have not had the coronavirus.
  • If you have never had COVID-19, you may notice more side effects after the second dose than after the first dose.

What are COVID booster side effects?

After getting an additional shot of a COVID-19 vaccine, you might experience side effects similar to those after your second dose of the vaccine.

Rare Side Effects of COVID Vaccines

Myocarditis and the COVID-19 Vaccines

Since April 2021, some people have developed myocarditis (inflammation of the heart muscle) and pericarditis (inflammation of the lining outside the heart) after receiving the Pfizer-BioNTech or Moderna coronavirus vaccines in the United States, according to the U.S. Centers for Disease Control and Prevention (CDC). The problem occurs more often in adolescents (teens) and young adults, and in males.

Considering the hundreds of millions of COVID-19 vaccine doses that have been administered, these reports are very rare. The vast majority of myocarditis or pericarditis cases are mild and resolve quickly. Myocarditis is more likely to occur as a result of COVID-19 infection than as a side effect of the vaccines.

Seek medical attention right away if, within a few days of receiving the second injection of an mRNA COVID-19 vaccination (Pfizer-BioNTech, Moderna), you or your child experience:

  • Chest pain
  • Shortness of breath
  • Feelings of having a fast-beating, fluttering or pounding heartbeat

COVID can cause heart problems, too

Having COVID-19 can also cause heart problems. One study published by the CDC reports that from March 2020 to January 2021, patients with COVID-19 had nearly 16 times the risk for myocarditis compared with patients who did not have COVID-19.

Blood Clots (TTS) and the Johnson & Johnson Vaccine

Due to potential blood clots following administration of the Johnson & Johnson vaccine, the CDC updated its recommendations in December 2021. The CDC noted that the two mRNA vaccines, from Pfizer and Moderna, are preferred over the Johnson & Johnson vaccine, which remains available for those who prefer it and for use in certain circumstances.

Women ages 30-49 years, especially, should be aware of the increased risk of this rare adverse event and should know that other COVID-19 vaccines are available.

If you receive a J&J vaccine, for three weeks, you should watch for possible symptoms of TTS and get medical help immediately if you have any of these symptoms:

  • Severe or persistent headaches or blurred vision
  • Shortness of breath
  • Chest pain
  • Leg swelling
  • Persistent abdominal pain
  • Easy bruising or tiny blood spots under the skin near the injection site

Is there risk of allergic reaction from COVID-19 vaccine?

According to the CDC, anyone who has a known severe allergy (e.g., anaphylaxis) to any of the vaccine ingredients should not receive that vaccine.

The CDC says people with allergies to certain foods, insects, latex and other common allergens can safely receive the COVID-19 vaccine. Those with a history of severe allergic reaction (anaphylaxis) to injectables or other vaccines should discuss the vaccination with their doctor, who can evaluate and assess their risk.

COVID-19 Vaccines Are Safe and Effective

Data show that the vaccines are very good at preventing serious or deadly cases of COVID-19 even after considerable time since completing vaccination. Overall, the benefits of being vaccinated are much greater than the risks involved.

Learn more about COVID-19 vaccine safety.

syringe close up - covid19 coronavirus vaccine

COVID-19 Vaccine

Get information and updates from Johns Hopkins Medicine.