- The Omicron variant remains the most dominant strain of COVID-19 in the U.S.
- Fortunately, both Pfizer and Moderna have developed a booster to protect against Omicron.
Ahead of a potential winter wave of COVID-19 infections, experts are urging people to get vaccinated and boosted against the dominant Omicron strain.
"It's still the main variant in the United States, and we expect it to remain that way for the foreseeable future," says Dr. Waleed Javaid, hospital epidemiologist and director of infection prevention and control at Mount Sinai Downtown.
The original vaccines, first introduced in late 2020, mostly protected against earlier strains of COVID-19 and provided limited protection against Omicron.
The most recent bivalent booster, manufactured by both Pfizer and Moderna, effectively protects against the Omicron variant, as well as earlier strains of COVID-19.
However, the Omicron booster, like other COVID vaccines, may also result in the same uncomfortable side effects like pain at the injection site and fatigue.
Below, we've outlined what to expect after getting the Omicron booster and how to cope if you don't feel well, according to public health experts.
Omicron booster side effects
The symptoms of the new booster are no different than previous COVID-19 vaccines, says Dr. Gabor David Kelen, director of the department of emergency medicine and director of the Johns Hopkins Office of Critical Event Preparedness and Response.
Most people start feeling unwell 6-12 hours after the shot, with symptoms lasting anywhere from 24-36 hours.
Below are four of the most common side effects of the Omicron booster:
1. Sore arm
Javaid says one of the most common side effects of the Omicron booster, or any vaccine, is soreness or tenderness in the area where the shot was injected.
2. Fever and chills
As your immune system responds to the vaccine, you may develop a low-grade fever or chills.
Research by the Centers for Disease Control and Prevention (CDC) suggests it's uncommon to develop a fever higher than 40º celsius (104º farenheit) after receiving the Omicron booster.
3. Muscle aches
Just as any viral illness can cause your whole body to hurt, Kelen says the Omicron booster can result in achy muscles and joints.
4. Fatigue
Many people complain of feeling tired after the Omicron booster. You might feel like going to bed, or you might feel mentally foggy.
Either way: "It's not unusual to feel astoundingly fatigued afterward," Kelen says.
What to expect after getting the Omicron booster
In general, you'll react to the Omicron booster the same way that you reacted to your other COVID-19 shots. "If you've had the original COVID-19 vaccines, you shouldn't expect anything different with this booster," Kelen says.
Kelen adds that people with compromised immune systems, such as elderly people or those taking steroids or undergoing chemotherapy, may have fewer side effects because their immune systems are weaker.
When you have a stronger immune system, you typically have a stronger immune response to vaccines, which is why older and immunocompromised populations may not react as strongly.
On the other hand, a recent study suggests people with worse side effects may have more protection against COVID-19, possibly because their immune systems developed a stronger antibody response.
How to find relief
First and foremost: Wait for symptoms to arise before taking any medication for relief.
Once symptoms arise, Kelen recommends Tylenol since medications that reduce inflammation (like NSAIDs) could also reduce your immune response. But Tylenol won't affect your immune system.
Important: Experts advise against taking NSAIDs like ibuprofen before your shot to prevent symptoms, "because they could suppress your immune response," Javaid says.
If your symptoms aren't resolving with Tylenol, then you can try to alleviate it with an NSAID, Kelen says.
Another tip: If your arm is bothering you, the CDC suggests applying a cool cloth to the area.
Try to get as much rest as possible, too, until you feel better. If possible, schedule your booster for a time when you'll actually be able to take it easy.
"We advise people to get their booster when they don't have to go to work or have backup for home responsibilities," says Kelen. "Try to time it with days off so you can rest."
Who should not get the Omicron booster
Javaid recommends the Omicron booster — and all COVID-19 vaccines — to everyone, including those with compromised immune systems. Recent research also confirms the booster is safe for pregnant and lactating individuals.
The only exception is if you've had a severe allergic response to a COVID-19 vaccine in the past, or if you know you're allergic to one or multiple of its ingredients.
"If you had an anaphylactic response to a COVID-19 vaccine, you might be allergic to some components, so talk to your medical provider about it," Javaid says.
The CDC recommends getting the Omicron booster if it's been at least two months since your last COVID-19 vaccine dose, whether your final primary series dose or a monovalent booster.
Important: The Omicron booster currently can't be used as the primary series dose, so if you haven't had a COVID-19 vaccine before but are considering it, you'll need to get a primary series vaccine first.
If you've recently had a positive COVID-19 test, Kelen says you may have antibodies for up to three months for that specific strain. So, theoretically, you could wait that long to get your booster. However, it's no guarantee that you won't contract another COVID strain in the meantime.
Therefore, if you want to ensure protection against multiple strains of the virus, Kelen says that you can get the Omicron booster at any time after your symptoms resolve.
Insider's takeaway
The Omicron booster can cause uncomfortable symptoms including sore arm, fatigue, fever, and muscle aches.
If you feel unwell after your Omicron booster, focus on self-care — and rest assured your immune system is hard at work.
"It means your immune system is actually reacting to it to develop immunity," says Kelen.