COVID-19: Vaccine FAQs

The vaccines now being used to help protect against COVID-19 have been tested and found to be safe and effective in preventing infection.

The U.S. Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention (CDC) currently recommend the shots for everyone ages 6 months and up, with additional booster shots recommended for ages 5 and up, if eligible. People with a history of severe allergic reactions to vaccines should consult with their healthcare provider before getting the COVID-19 vaccine to determine whether it’s safe for them.

Below are 10 FAQs about the vaccines. Decisions about vaccine eligibility, booster doses and other info about COVID-19 change frequently. For the most updated info, visit the CDC’s COVID-19 webpages.

Safety & Effectiveness

What is the COVID-19 vaccine and how can I be sure it is safe?

The COVID-19 vaccine is medicine injected into your upper arm that teaches your immune system to produce antibodies that fight off the virus if you’re exposed to it.

The vaccines will not make you sick with COVID-19, and if you do end up getting the virus after being vaccinated, you will likely have a milder illness. Learn more about how these vaccines work.

Hundreds of millions of people have been vaccinated for COVID-19 in the U.S., and the vaccines are undergoing the “most intensive safety monitoring in U.S. history,” according to the CDC.

Following rigorous standards for safety, effectiveness and quality, the FDA and CDC have authorized a primary COVID-19 vaccine series. These differ by age and vaccine type:


  • Ages 6 months through 4 years – 3 doses; the first 2 doses given 3-8 weeks apart and the 3rd dose at least 8 weeks after the 2nd dose.
  • Ages 5 and up – 2 doses given 3-8 weeks apart.


  • Ages 6 months through 5 years – 2 doses given 4-8 weeks apart.
  • Ages 6-17 – 2 doses given 4-8 weeks apart.
  • Ages 18 and up – 2 doses given 4-8 weeks apart

Johnson & Johnson (J&J) Janssen:

  • Ages 6 months through 17 years – The J&J vaccine is currently not authorized for this age group.
  • Ages 18 and up – 1 dose
  • Note: The J&J vaccine has been linked to a rare, but serious blood clot risk in a small number of people. It’s considered safe for the vast majority and is still authorized, particularly for people unable to have one of the other 2 available vaccines. But the CDC has said that in most situations, the Pfizer and Moderna vaccines are preferable.


  • Ages 6 months through 11 years – The Novavax vaccine is currently not authorized for this age group.
  • Ages 12 and up – 2 doses given 3-8 weeks apart

For kids and adults with weakened immune systems: If you or your child are moderately or severely immunocompromised from another health condition, an additional dose of the primary COVID-19 vaccine series may be recommended. Learn more here.

COVID-19 Booster Shots: While the primary vaccines are considered highly effective, the CDC and FDA have authorized booster shots for most people ages 18 and up, when eligible, to help deal with reduced immunity over time. A booster shot is not currently recommended for people who received the Novavax vaccine. Booster shot recommendations for children vary by age and vaccine type. Learn more about booster shots.

Vaccines remain the safest, most effective protection we have against serious diseases. Learn more about their safety and importance.

If I already had COVID-19, do I still need to be vaccinated?

Yes. It is possible that you could be infected again. If you were treated for COVID-19 and have recovered, ask your doctor when you can get vaccinated. People who currently have COVID-19 should wait until recovery before getting the vaccine.

Can my children get vaccinated?

Children and teens ages 6 months and up can now be vaccinated for COVID-19, and the CDC and FDA strongly recommend this. The child dosage for the vaccine is smaller than the adult dosage, based on testing for safety and effectiveness. See “What is the COVID-19 vaccine and how can I be sure it is safe?” above for details.

While most children infected with the virus have had either mild or no symptoms, many have been hospitalized with more severe illness—and some have died. Infants under age 1 and children with medical conditions that have weakened their immune systems have a higher risk of more severe illness with COVID-19.

If I’m pregnant or breastfeeding, can I get this vaccine and will it be safe for my baby?

Yes. The CDC, American College of Obstetricians and Gynecologists, and the Society for Maternal-Fetal Medicine all recommend the COVID-19 vaccine for people who are pregnant or breastfeeding. The CDC also recommends vaccination for individuals planning to become pregnant now or in the future.

Pregnant women are at increased risk for severe illness from COVID-19. Researchers are still studying whether infection from the virus during pregnancy affects the fetus or causes problems later in the child’s life.

The CDC notes that vaccine monitoring data so far suggests that the protective benefits of COVID-19 vaccines outweigh any potential risks of vaccination during pregnancy.

Monitoring and research so far has shown no evidence that the vaccines cause fertility problems in women or men, or are harmful during pregnancy or when breastfeeding—to the pregnant or lactating person, developing fetus or breastfed infant.

If you’re pregnant or breastfeeding, talk with your healthcare provider about the COVID-19 vaccine—and know how to protect yourself if you decide against vaccination. Stay in-the-know about the vaccine by checking in regularly with the CDC’s COVID-19 vaccine info page.

Getting the Vaccine

When can I get this vaccine?

The COVID-19 vaccine is now available for everyone, ages 6 months and up, in the U.S. Use the resources here to locate a vaccine site and learn how to schedule an appointment. For young children, you may also want to check in with your family healthcare provider about vaccine availability.

How many doses will I need and how long will my immunity last?

The Pfizer-BioNTech vaccine requires 2 doses for ages 5 and up and 3 doses for ages 6 months through 4 years. Moderna requires 2 doses for ages 6 months and up. The J&J vaccine requires 1 dose but is only authorized for ages 18 and up. The Novavax vaccine requires 2 doses but is only authorized for ages 12 and up. All vaccines are given by injection. See “What is the COVID-19 vaccine and how can I be sure it is safe?” for info on doses by age group and vaccine type.

Additional booster doses are recommended for all but the Novavax vaccine, depending on your age. Learn more about the booster shots and eligibility.

The CDC is monitoring the vaccines’ effectiveness, including how long immunity from COVID-19 lasts.

Does the vaccine have side effects?

Side effects from the COVID-19 vaccines have been mild for the vast majority of people. Serious side effects are extremely rare. Younger children may have fewer side effects than teens or adults. Learn more here.

Side effects have generally included pain and/or swelling at the injection site, fever, chills, fatigue and muscle aches. These may feel a bit like the flu for some and could interfere with daily activities. But they should go away in a few days. For some relief in the meantime:

  • Ask your healthcare provider if you can take an over-the-counter pain and fever reliever (ibuprofen or acetaminophen).
  • Apply a cool, damp cloth to the injection site to relieve any soreness.
  • Dress lightly and drink plenty of fluids for relief from fever discomfort.

If you are pregnant and get a fever after a dose of the COVID-19 vaccine, the CDC recommends taking acetaminophen (Tylenol), according to dosage instructions. This is because any fever (whatever the cause) during pregnancy may raise the risk of adverse pregnancy outcomes.

If you have increasing soreness at the injection site or side effects that persist even after a few days, contact your healthcare provider.

A severe allergic reaction, including anaphylactic shock, in response to the vaccine is possible but quite rare. So far, this has only occurred in people with a history of severe allergic reactions (such as anaphylactic shock) to other vaccines. The COVID-19 vaccine is not recommended for these people.

How much will it cost, and can I choose which vaccine I receive?

The vaccine is currently free, but your pharmacy or healthcare provider may charge a fee to administer the shot. Your insurance company can reimburse this fee. If you’re not insured, you can request reimbursement from the Health Resources and Services Administration’s Provider Relief Fund.

As for being able to choose which vaccine you or your child receive, this will likely depend on both availability and eligibility for each particular vaccine.

Life After Vaccination

Will I still need to wear a face mask and avoid close contact with others after getting the vaccine?

At first, yes. Depending on your age and the vaccine you receive, you may need 2 or 3 doses (several weeks apart). Once fully vaccinated, it takes 2 weeks for your body to build immunity to COVID-19.

Once you have that immunity (after being fully vaccinated), the FDA and CDC have authorized additional booster shots to deal with weakening immunity over time. Learn more about the booster shots and eligibility for them.

The CDC recommends wearing a mask in potentially crowded indoor public settings, and particularly when you’re in an area with high rates of COVID transmission.

Mask-wearing around people you know are immunocompromised is also advised. Otherwise, you can resume activities without wearing a mask or social distancing—except where required by laws, rules or regulations (such as in certain businesses, hospitals or other locations).

If you are exposed to or test positive for COVID-19, regardless of your vaccination status, check here for CDC guidance on what to do.

How many people need to get vaccinated for us all to return to normal life?

While there are reports that at least 70% of the U.S. population will need to be vaccinated to achieve herd immunity, the CDC has been careful to say the answer is not yet known. Herd immunity occurs when enough people are protected (either by vaccination or previous infection) that it’s unlikely a virus can spread.

Public health officials are monitoring vaccinations and the continuing spread of COVID-19 to determine when herd immunity has occurred.

This message is not intended to provide individual medical advice. Always seek the advice of a physician or qualified healthcare provider for any questions you have about your health or medical condition, your breastfeeding issues and your infant's health. Never disregard, avoid or delay contacting a doctor or other qualified professional because of something you have read in our emails, webpages or other electronic communications.

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