These Are the Most Common Side Effects of the Omicron COVID-19 Booster Shot

·5 min read
These Are the Most Common Side Effects of the Omicron COVID-19 Booster Shot


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Earlier this month, the Food and Drug Administration (FDA) authorized the bivalent COVID-19 booster, also known as the Omicron COVID booster. Now, the booster shot is widely available in major pharmacies like CVS and Walgreens, as well as primary care doctor’s offices. If you’re headed to get yours, it’s only natural to wonder what the Omicron COVID booster side effects are, and what experts say to expect.

But before we dive into side effects, and in case you’re not familiar with this booster, it contains components of the original virus strain and the Omicron variant, per the Centers for Disease Control and Prevention (CDC). That’s why it’s called a bivalent COVID-19 vaccine. There isn’t a lot of data yet about the vaccines’ efficacy or side effects, but they’re designed to target the dominant Omicron subvariants, BA.4 and BA.5. It’s important to note, though, that the FDA did a thorough review of the data before granting emergency use authorization to the vaccines.

And since you actually can’t get the Omicron booster if you’ve never been vaccinated against COVID-19 with an original vaccination series, you probably have at least some knowledge of COVID vaccine side effects. However, the bivalent COVID-19 booster is slightly different—it has a tweaked code from previous booster shots and a lower dose than the primary vaccination shots.

So, what side effects can you expect with the Omicron booster? Experts break it down.

Omicron COVID-19 booster side effects

While the Omicron boosters have been lumped together, it’s important to point out that there are actually two options—a booster made by Moderna and one from Pfizer-BioNTech. Both bivalent vaccines target the original strain of SARS-CoV-2, along with Omicron subvariants (including BA.4 and BA.5, which are currently dominant in the U.S.).

But, of course, nearly everything in medicine has potential side effects. These are the most common ones you can expect with the Omicron booster vaccines, according to the FDA:

  • Pain at the injection site

  • Redness and swelling at the injection site

  • Fatigue

  • Headache

  • Muscle pain

  • Joint pain

  • Chills

  • Swelling in the lymph nodes in the same arm as the injection

  • Nausea and vomiting

  • Fever

If you’ve already had a booster shot of a COVID-19 vaccine, you can expect more of the same potential side effects, says infectious disease expert Amesh A. Adalja, M.D., a senior scholar at the Johns Hopkins Center for Health Security. “It’s unlikely there will be a major difference in side effects with Omicron-targeted boosters,” he says.

Something else to keep in mind, per Thomas Russo, M.D., professor and chief of infectious disease at the University at Buffalo in New York: The Moderna vaccine tends to be more likely to cause side effects than the Pfizer-BioNTech vaccine. But, he says, there are other factors at play. “The younger you are, the more likely you are to have symptoms,” he says. “Females are also more likely to have reactogenic symptoms than males.”

Still, Dr. Russo says, “Everyone is different. In any given individual, you don’t know what the side effects will be.”

How do bivalent Omicron booster side effects compare to primary vaccination series side effects?

You’re usually less likely to have side effects with a booster shot than you are with a primary vaccination series, Dr. Russo says. This, he says, is usually because the dose is lower.

However, you can have similar side effects with a COVID-19 booster as you had with your original vaccination series. The Centers for Disease Control and Prevention(CDC) lists the following as potential side effects of getting the COVID-19 vaccine:

  • Pain at the injection side

  • Redness and swelling at the injection site

  • Tiredness

  • Headache

  • Muscle pain

  • Chills

  • Fever

  • Nausea

But again, everyone is different. “All bets are off for a given individual on a given day,” Dr. Russo says.

You could get your Omicron booster shot and feel just fine afterward, or you may end up feeling a little out of sorts for a few hours, Dr. Russo says.

“People should play it by ear and determine whether they need to take a day off or not,” Dr. Adalja says. “It will vary and using prior vaccine experiences is generally a good guide.” Meaning, if you felt just fine after your last booster dose, odds are high you’ll experience the same this time around.

What to do if you have side effects from your bivalent COVID-19 booster

The CDC recommends that you do the following to feel better if you have side effects from the vaccine:

  • Try to take it easy and, if possible, get some rest

  • Drink plenty of fluids

  • Take over-the-counter medication like ibuprofen, acetaminophen, aspirin, or antihistamines if you’re uncomfortable

  • Apply a clean, cool, wet washcloth over your arm if you have redness or swelling

  • Use or exercise your arm to reduce discomfort

If you have side effects from the Omicron booster, Dr. Russo recommends that you try to look at the big picture. “These symptoms are a sign that your body is reacting to the vaccine,” he says. “Side effects usually resolve fairly quickly—within 24 hours or less.”

This article is accurate as of press time. However, as the COVID-19 pandemic rapidly evolves and the scientific community’s understanding of the novel coronavirus develops, some of the information may have changed since it was last updated. While we aim to keep all of our stories up to date, please visit online resources provided by the CDC, WHO, and your local public health department to stay informed on the latest news. Always talk to your doctor for professional medical advice.


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