Frequently Asked Questions About Vaccine Safety

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Are the COVID-19 vaccines safe?

Yes. The COVID-19 vaccines available in the United States meet the FDA’s rigorous standards for safety and effectiveness. Tens of millions of people in the United States have received COVID-19 vaccines, and all COVID vaccines will continue to be monitored for safety.

Serious health effects from vaccines are very rare. It’s highly unlikely that COVID-19 vaccines will cause long-term health problems. Also, there is no evidence at all that they will cause cancer or fertility problems in women or men.

Your risk for serious health problems is much lower from the vaccine than your risk if you’re unvaccinated and get COVID-19. COVID-19 can leave you with heart and lung damage and other conditions that require long-term treatment. Vaccines are much safer paths to immunity than the disease itself.

How can COVID-19 vaccines be safe since they were developed so fast?

Safe COVID-19 vaccines were developed quickly through the use of a century of vaccine experience; technology that was new to vaccines but had been studied for two decades; a coronavirus vaccine already in development at the National Institutes of Health; and tens of thousands of volunteers for clinical trials that enabled rapid accumulation of data on safety and effectiveness. Simultaneous vaccine production and analysis of testing data also allowed vaccines to be shipped within days of FDA authorization.

Will the shot hurt or make me sick?

Some people might get sore muscles, feel tired, or have mild fever after getting the vaccine, but most people report only a sore arm where they got the shot. These reactions mean the vaccine is working to help teach your body how to fight COVID-19 if you are exposed. For most people, these side effects will go away on their own in a few days. If you have any concerns, call your doctor or nurse.

Why are people having allergic reactions to the COVID-19 vaccine?

A few people have had allergic reactions called anaphylaxis after getting a COVID-19 vaccine but were treated and have recovered. Your doctor can help you decide if it’s safe for you to be vaccinated.

How do COVID-19 vaccines work?

Vaccines train your immune system to recognize and fight the virus that causes COVID-19. With vaccines, you can build immunity to a disease without getting the disease.

How effective are the COVID-19 vaccines?

All available COVID-19 vaccines are highly effective against severe illness, hospitalization, and death due to COVID-19, including from the Delta variant.

Remember, to get the most protection from the vaccines, you need all the recommended doses:

  • The Pfizer-BioNTech and Moderna vaccines require two initial doses.
  • Johnson & Johnson’s Janssen vaccine requires one initial dose.

If you meet the criteria for having a compromised immune system, you should get a third dose of the Pfizer-BioNTech or Moderna vaccine at least 4 weeks after your second dose. An FDA and CDC review of data for Johnson & Johnson’s Janssen vaccine will determine whether a second dose is appropriate for people with compromised immune systems.

Why should I get vaccinated if I can still get infected with COVID-19?

It’s important to understand that infection doesn’t necessarily lead to illness. If you’re fully vaccinated against COVID-19 and the virus manages to enter your body and begins to multiply—that is, infect you—your immune system will be prepared to quickly recognize the virus and keep it from doing real damage. That’s why most people who get infected with COVID-19 despite being vaccinated—so-called breakthrough cases—have no symptoms (asymptomatic) or only mild-to-moderate illness.

Nearly everyone in the United States who is getting severely ill, needing hospitalization, and dying from COVID-19 is unvaccinated.

CDC recommends you get vaccinated as soon as you can.

How long do COVID-19 vaccines last?

Scientists don’t know right now how long COVID-19 vaccines protect people, but they are investigating this in medical studies.

Do I need to get a COVID-19 vaccine if I’ve already had COVID-19?

Yes. Scientists don’t yet know how long natural antibodies in people who have had COVID- 19 will be protect them from being reinfected.

Will the COVID-19 vaccines prevent me from infecting others?

COVID-19 vaccines reduce the likelihood that you’ll develop and be able to spread COVID-19. In rare occasions, some vaccinated people can get COVID-19 from the highly contagious Delta variant and spread it to others. Importantly, only a very small amount of spread happening around the country comes from vaccinated individuals.

Do the vaccines work on the new COVID variants?

Scientists continue to study different forms, or variants, of the virus that causes COVID-19 to see if the vaccines will work against them. Current data suggest that all COVID-19 vaccines recommended for use in the United States offer protection against most variants, including the highly contagious Delta variant.

When can I get a COVID-19 vaccine?

Vaccines are here now and everyone age 12 and older can get them. You have three ways to find vaccines near you:

  • Go to vaccines.gov
  • Text your ZIP code to 438829
  • Call 1-800-232-0233

How much will a COVID-19 vaccine cost?

The federal government is providing the vaccine free of charge to all people in the United States.

Do I need to wear a mask after getting vaccinated?

If you’re fully vaccinated, you can participate in many of the activities that you did before the pandemic. To maximize protection from the highly contagious Delta variant and prevent possibly spreading it to others, wear a mask inside public places if you’re in an area of substantial or high spread of COVID-19.

If you’re not yet vaccinated, you should continue to:

  • Wear a mask when inside public places.
  • Keep at least 6 feet apart from people who don’t live with you and who may not be vaccinated.
  • Avoid crowds.
  • Avoid poorly ventilated spaces.
  • Wash your hands often with soap and water for at least 20 seconds or use hand sanitizer with at least 60% alcohol when soap and water are not available.

Vaccinated and unvaccinated people must still follow federal, state, local, tribal, and territorial laws, rules, and regulations. That includes public transportation, airport/airplane, local business, and workplace guidance.

Do people with compromised immune systems need extra doses of a COVID-19 vaccine?

People with compromised immune systems are less able to fight infections. If any of the following apply to you, you may not be fully protected from COVID-19 even if you’ve received two doses of Pfizer-BioNTech’s or Moderna’s mRNA COVID-19 vaccine:

  • You have a moderate or severe primary immunodeficiency disorder, such as DiGeorge syndrome or Wiskott-Aldrich syndrome.
  • You have an advanced or untreated HIV infection.
  • You’ve ever had an organ transplant or had a stem cell transplant within the last 2 years.
  • You’re being treated with corticosteroids or other immunosuppressant medicines for such conditions as arthritis, asthma, or an autoimmune disease, such as lupus, sarcoidosis, inflammatory bowel disease, rheumatoid arthritis, and psoriasis.
  • You’re being treated for cancer.

To get the most benefit from the mRNA COVID-19 vaccines, people with compromised immune systems should get a third dose. Wait at least 4 weeks after you get your second dose to get your third dose. An FDA and CDC review of data for Johnson & Johnson’s Janssen vaccine will determine whether a second dose is appropriate for people with compromised immune systems.

You should also continue to follow current COVID-19 prevention measures until your health care provider says it’s safe for you to stop:

  • Wear a mask that covers your nose and mouth around people you don’t live with and when inside public places.
  • Stay at least 6 feet apart from people you don’t live with.
  • Avoid crowds and poorly ventilated indoor spaces.
  • Wash your hands often with soap and water for at least 20 seconds or use hand sanitizer with at least 60% alcohol when soap and water aren’t available.