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Complete Guide to COVID-19 Booster Shots

Everything you need to know about getting an extra dose of the Pfizer, Moderna or J&J vaccine

vials of covid booster shots with an illustration of cells

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Booster shots for all three COVID-19 vaccines have received the green light from federal health officials, and millions of Americans are eligible for the extra dose to enhance protection from severe illness.

Here’s what you need to know about getting a booster from Pfizer-BioNTech, Moderna or Johnson & Johnson before rolling up your sleeve.

Pfizer

Pfizer’s mRNA booster has been available to millions of Americans since Sept. 24, as it was the first of the three COVID-19 vaccine boosters to pass regulatory hurdles from the Food and Drug Administration (FDA) and Centers for Disease Control and Prevention (CDC). 

Who qualifies?

  • Adults 18 and older who were vaccinated with two doses of Pfizer's COVID-19 vaccine at least six months ago.
  • Adults 18 and older who were vaccinated with two doses of Moderna’s COVID-19 vaccine at least six months ago. 
  • Adults 18 and older who were vaccinated with Johnson & Johnson’s single-shot COVID-19 vaccine at least two months ago.  

When can you get it?

If you were vaccinated with either Pfizer or Moderna’s two-dose series: You can get Pfizer’s booster at least six months after the second shot.

If you were vaccinated with Johnson & Johnson (J&J): You are eligible for Pfizer’s or Moderna's booster shot at least two months after your initial J&J vaccine.  

What are the side effects?

Pfizer’s booster is the same formulation and dosage as the first two shots in the series. And clinical trial data shows the side effects from it are similar to those many experienced the first time around, the most common being:

  • Injection site pain
  • Fatigue
  • Headache
  • Muscle pain
  • Chills

These symptoms are usually mild to moderate in severity and typically resolve in a few days. More than 228 million Americans have received at least one dose of a COVID-19 vaccine, and so far, no long-term side effects have been detected, the CDC says.

What are the rare reactions associated with this vaccine?

More serious side effects can occur but are rare. Anaphylaxis, a severe allergic reaction, is one example. A small number of people have experienced this after getting vaccinated against COVID-19. However, anaphylaxis can happen after any vaccination, and vaccine providers should be able to treat it quickly.

Need help getting a COVID-19 vaccine or booster?

Visit vaccines.gov or call 1-800-232-0233 (TTY: 888-720-7489) for assistance in English, Spanish, and many other languages.

Myocarditis (inflammation of the heart muscle) and pericarditis (inflammation of the sac that surrounds the heart) have been linked to the mRNA vaccines (Pfizer and Moderna). Cases have mostly been reported in males under 30, more often after the second dose. Symptoms — chest pain, shortness of breath, feelings of having a fast-beating, fluttering, or pounding heart — can pop up several days after vaccination. Experts stress these events are rare and people usually recover quickly with medical care and rest.

Can I get boosted with another brand?

Yes. If you qualify for Pfizer’s booster but don’t have access to it or want to get a booster from Moderna or J&J, that is an option, based on new guidance from the FDA and CDC.

Preliminary results from a federally funded study show that while boosters from all three manufacturers (Pfizer, Moderna and J&J) enhance antibody levels, getting boosted with a vaccine from a different manufacturer can have a more pronounced effect on immune response. What’s more, the study showed no new or concerning side effects from mixing and matching.  

If you’re thinking of mixing up your booster it’s a good idea to talk to your doctor first, says Mohammad Sobhanie, M.D., an infectious disease expert at the Ohio State University Wexner Medical Center. “I think it's incredibly important that you have these conversations with your primary care physician so that they can give you the best advice out there based on your medical conditions,” he says. 

Getting a booster? What to know:

  • Just like with the initial COVID-19 vaccines, there are no out-of-pocket costs to get a booster shot; no insurance or ID is required.
  • You can find booster shots where you find the COVID-19 vaccines — pharmacies, doctor’s offices, community health clinics, etc. You may need an appointment, so check in on the details.
  • It’s a good idea to call ahead of time to confirm the location has the booster brand you want to receive.
  • Bring your COVID-19 vaccine card so it can be updated to include your booster. Lost it? Here’s some advice on what to do.
  • You may experience some mild to moderate side effects after your booster — the most common are fatigue and pain at the injection site.

Moderna

Moderna’s booster is available to the same groups that qualify for Pfizer’s shot, including:

  • Adults 18 and older who were vaccinated with two doses of Pfizer's COVID-19 vaccine at least six months ago.
  • Adults 18 and older who were vaccinated with two doses of Moderna’s COVID-19 vaccine at least six months ago.
  • Adults 18 and older who were vaccinated with Johnson & Johnson’s single-shot COVID-19 vaccine at least two months ago.

When can you get it?

If you were vaccinated with either Pfizer’s or Moderna’s two-dose series: You can get Moderna’s booster at least six months after the second shot, meaning many people who were vaccinated last winter and early spring can go ahead and get boosted.

If you were vaccinated with Johnson & Johnson (J&J): You are eligible for Moderna’s booster shot at least two months after your initial J&J vaccine.

What are the side effects? 

Moderna’s booster shot is different from Pfizer's and J&J’s boosters because it is half the dose (50 micrograms) of the initial vaccine.

Even still, studies show the side effects of this smaller dose are similar to those many experienced after shots one and two in the series, the most common being:

  • Injection site pain
  • Fatigue
  • Headache
  • Muscle pain
  • Joint pain

Swollen lymph nodes in the underarm were observed more frequently following Moderna’s booster dose than after the primary two-dose series, according to the FDA.

What are the rare reactions associated with this vaccine?

Just like Pfizer’s vaccine, Moderna’s product has also been linked to myocarditis (inflammation of the heart muscle) and pericarditis (inflammation of the sac that surrounds the heart). These cases are rare and have mostly occurred in young men (30 and under) after the second vaccine dose.

Other serious side effects can occur, but are rare, including anaphylaxis, which is a severe allergic reaction that can happen after any vaccination.

Can I get boosted with another brand?

Yes. If you qualify for Moderna’s booster but don’t have access to it or want to get a booster from Pfizer or J&J, that is an option, based on new guidance from the FDA and CDC.

Preliminary results from a federally funded study show that mixing and matching vaccine boosters can produce a higher level of antibodies, which is one measure of immune response, and no safety concerns were identified.  

Giving the green light for people to mix and match the products also makes getting the booster more convenient, especially in areas where options may be more limited. However, if you’re thinking of mixing up your booster it’s a good idea to talk to your doctor first, experts say.


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Johnson & Johnson  

Johnson & Johnson’s booster shot is now available to millions. It uses a different technology from Pfizer's and Moderna’s mRNA vaccines, called a viral vector. Here’s what you need to know:

Who qualifies?

J&J’s booster is available to:

  • Adults 18 and up who had the J&J vaccine, also known as the Janssen vaccine, at least two months ago.
  • People 18 and older who were vaccinated at least six months ago with either Pfizer's or Moderna’s vaccine

When can you get it?

If you were vaccinated with either Pfizer’s or Moderna’s two-dose series: You can get J&J’s booster at least six months after your second shot in the mRNA series.

If you were vaccinated with Johnson & Johnson (J&J): You are eligible for J&J’s booster at least two months after your initial vaccine.

What are the side effects?

Just like with Pfizer and Moderna, some clinical trial participants reported mild to moderate side effects after the J&J booster, the most common being:

  • Injection site pain
  • Fatigue
  • Headache
  • Muscle pain
  • Nausea

What are the rare reactions associated with this vaccine?

rare event called thrombosis with thrombocytopenia syndrome (TTS) has been associated with the J&J vaccine. Most reports of this serious condition, which involves blood clots with low platelets, have been in women younger than 50, according to the CDC. Health officials say that the benefits of the vaccine still outweigh the risks, but that young women “especially should be aware of the rare but increased risk of this adverse event, and they should know about other available COVID-19 vaccine options for which this risk has not been seen.”

The CDC and FDA are also monitoring reports of Guillain-Barré Syndrome in people who have received the J&J vaccine. This rare disorder can lead to muscle weakness and sometimes paralysis from which most people recover. There have been around 233 preliminary reports of Guillain-Barré identified out of more than 15.2 million J&J vaccine doses administered; most have been in men 50 and older.

Can I get boosted with another brand?

Yes. If you had J&J’s vaccine at least two months ago and want to get a booster from either Pfizer or Moderna, that is an option, based on new guidance from the FDA and CDC.

Preliminary results from a federally funded study show that mixing and matching vaccine boosters can produce a higher level of antibodies — especially among J&J vaccine recipients who were boosted with an mRNA vaccine. What’s more, no safety concerns were identified.

However, if you’re thinking of mixing up your booster it’s a good idea to talk to your doctor first, experts say.

Rachel Nania writes about health care and health policy for AARP. Previously she was a reporter and editor for WTOP Radio in Washington, D.C. A recipient of a Gracie Award and a regional Edward R. Murrow Award, she also participated in a dementia fellowship with the National Press Foundation.