Best COVID-19 Booster Shot: Pfizer, Moderna, or Novavax?

By Dr Frank Yap, M.D. - October 26, 2022

The first COVID-19 vaccines were authorized in December 2020. Fast forward to almost 2 years later, there’s been a world of change. Four different COVID-19 vaccines are authorized or approved for use, vaccines are widely available at pharmacies across the U.S., and millions of doses have been administered.

Three of these vaccines, Pfizer, Moderna, and Novavax, are also recommended as booster shots. The Pfizer and Moderna vaccines initially targeted the original strain of the virus, but updated versions are now available. These updated (bivalent) booster shots target both the original SARS-CoV-2 virus and the Omicron BA.4/5 subvariants. They aim to offer more protection against current variants that are making people sick. The Novavax vaccine is a monovalent vaccine that targets the original virus strain.

Still, with new information, data, and recommendations coming from many different sources, it’s hard to know what to do for your next shot. Ever-changing guidelines can be tough to digest, too. So, you may be thinking: “What do I really need to know about which vaccine is best for me?”

Who is eligible for a COVID-19 booster shot?

Booster shots are helpful because protection from a vaccine can lessen over time. The level of protection you had after becoming fully vaccinated may drop over the course of several months, so booster shots can help “boost” your protection back up to an adequate level.

At this time, everyone ages 5 and older in the U.S. is eligible to get a COVID-19 booster shot. No matter which vaccine(s) you initially received for your primary series, here are the current CDC-backed booster shot recommendations.

At this time, booster shots aren’t authorized for people age 4 or younger. Kids ages 6 months through 4 years of age are eligible for their primary vaccine series only.

Credit: GoodRx.com

What about second booster shots?

Before the FDA authorized updated Omicron-fighting Pfizer and Moderna booster shots, they allowed certain people to get second booster shots at least 4 months after their initial boosters. Based on predicted immune protection from their initial vaccine doses, the following people qualified for them:

Adults ages 50 and older
Adults who received two doses of the J&J vaccine
Certain people ages 12 and older who are immunocompromised

Going forward, the recommendations for booster shots are more simple. You can get an updated booster shot 2 months after you’ve completed your primary vaccine series or last booster dose.

However, there’s an exception with the Novavax vaccine. Novavax is only authorized as an initial booster. It’s not authorized as a second or third booster shot. You can get it 6 months after you finish your primary series. And it’s reserved for people who can’t or don’t want to receive the Pfizer or Moderna shots.

Does your COVID-19 booster shot need to be the same as your original vaccine?

It can be, but it doesn’t have to be.

The FDA and CDC are allowing a “mix-and-match” approach for COVID-19 booster shots. This means that regardless of the vaccine that you received first, you can choose the vaccine that you want next.

For example, if you initially received the original Pfizer COVID-19 vaccine for your primary series, you can choose which vaccine you want for your updated booster shot. You could decide to get Pfizer again, or you could choose to get Moderna. The Novavax vaccine is another option if you haven’t received any boosters yet.

That said, the J&J vaccine should not be used as a booster shot. The CDC issued a statement in late 2021 advising eligible people to get the Pfizer or Moderna booster shots if available, instead of the J&J vaccine. This statement followed a CDC expert panel meeting that reviewed updated data on a rare but serious blood clot risk linked to the vaccine.

Are COVID-19 booster shots the same as the original vaccine?

For Pfizer and Moderna, no. The original vaccines target the original strain of SARS-CoV-2, the virus that causes COVID-19. This is the strain that was first discovered in 2019. Now, for people ages 5 and older, COVID-19 booster shots are available as bivalent vaccines. They target the original virus strain and the Omicron BA.4/5 subvariants. Since Omicron has been the predominant variant in the U.S. for months, these updated (bivalent) vaccines may help offer more protection against the current virus that’s making people sick.

The Moderna vaccine has another layer. The booster shot for adults is half the dose of the original vaccine. When you get your first two doses of the Moderna vaccine, you receive 100 mcg of mRNA in each shot. But with the booster(s), you only receive 50 mcg. And kids ages 6 through 11 only receive 25 mcg.

On the other hand, the Novavax vaccine is the same regardless of whether it's used as your primary series or booster shot.

What risks are associated with COVID-19 boosters?

Research has shown that COVID-19 booster shots can help provide additional protection against COVID-19.

But that doesn’t mean they’re free of any risks. Risks of COVID-19 booster shots resemble the risks of previous vaccine doses. These can include:

Common side effects: Booster shot side effects seem to be similar to side effects you may have felt from your initial dose(s). This can include tiredness, fever, and pain or swelling where you received the shot.
Heart concerns: The Pfizer, Moderna, and Novavax vaccines have been connected to myocarditis (heart inflammation) and pericarditis (heart lining inflammation). This risk, while rare, has been reported most frequently in adolescents and young men. Research suggests that this risk may be higher for the Moderna vaccine than the Pfizer vaccine, but this isn’t totally certain.

Researchers will continue to study the effects of COVID-19 vaccines, especially since the Pfizer and Moderna vaccines are now available as new, bivalent formulations.

Which booster should you get?

Adults and kids ages 6 and older can get either an updated Pfizer or Moderna vaccine as their next booster shot, but kids who are as young as 5 years old can only receive the updated Pfizer booster at this time. The CDC recommends either of these vaccines for boosters. They don’t prefer one over the other.

What’s more, the Novavax vaccine is another option for adults ages 18 and older. It’s a good option if you can’t have, don’t want, or don’t have access to the updated Pfizer or Moderna vaccines. It’s considered to be an alternative option.

To help narrow down your choice between the three, you should weigh your options when deciding what course of action is best for you. You can also talk to your healthcare provider for their recommendation on your individual situation.

If you don’t feel strongly about one vaccine, the best move is to get a booster as soon as you can. Differences between the vaccines — especially when it comes to Pfizer and Moderna — are small and nuanced. The best shot is the one that you have access to.

But there are still a few thoughts to consider when making this decision. A summarized list of considerations are detailed below.

Sticking with the same vaccine

If you want your booster shot to be the same as your original vaccine, there’s logic to back up your decision.

For one, vaccine recommendations are complex and change frequently. With some exceptions, a safe move may be to stick with the same vaccine that you got originally.

It’s also likely that researchers will continue to conduct studies that look at how effective the same vaccine is over time. For example, it would make sense for Pfizer to see how effective their booster shot is following their own vaccine. They’d be less likely to research how effective the Moderna shot is following two doses of a Pfizer vaccine. However, some researchers have conducted “mix-and-match” effectiveness studies.

Separately, if you’re worried about infertility, don’t fret. There’s not any evidence that suggests any COVID-19 vaccines cause infertility in men or women. This shouldn’t sway your decision to choose a different vaccine.

Changing to a different vaccine

If you want your booster shot(s) to be different from your original vaccine, that would also make sense.

If you originally got the Pfizer vaccine, switching to the Moderna vaccine has been shown to result in a good immune response. The same goes for switching to Pfizer if you originally got Moderna. Some “mix-and-match” studies have found that getting a different booster may even lead to a slightly better immune response than getting the same vaccine again. However, the data isn’t fully clear. There isn’t a clear advantage to switching between the Pfizer and Moderna vaccines.

If you originally received the J&J vaccine, then you should switch to a different vaccine for your booster. If you received a J&J shot originally, current evidence suggests that a different vaccine booster shot provides more protection than another J&J vaccine. And even though the risk of developing blood clots with the J&J vaccine is low, it’s still possible.

Other considerations

Effectiveness data changes frequently. Based on current vaccine effectiveness data, you may be inclined to choose one vaccine over another. New studies about vaccine effectiveness come out many times a month. Plus, we don’t know a whole lot yet about how the benefits of the updated vaccines will compare to the original vaccines. We’ll learn more as time goes on.

The most up-to-date information may be helpful when deciding if you want to get a different vaccine from what you got originally. When it’s time to get your booster dose, try to look around and see what vaccine is best supported at the time. If you aren’t sure, ask a pharmacist or healthcare provider.

The bottom line

COVID-19 booster shots are currently available for people age 5 and older. For people ages 5 and older, you can get an updated vaccine booster if it’s been 2 months since you received both primary doses of your initial vaccines or last booster shot. Adults ages 18 and older can also get the Novavax vaccine as their initial booster shot.

If you’re still unsure which vaccine would be best for you, you should speak to your healthcare provider. They can help you weigh your options. If you want to schedule a booster dose, find a location near you by calling 1-800-232-0233 or by visiting Vaccines.gov.

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