Novavax (NVX-CoV2373) is a vaccine used to reduce the risk of serious infection from the virus that causes COVID-19. Novavax can cause side effects that range from mild to serious. Examples include muscle pain and blood clots.

Specifically, Novavax received emergency use authorization (EUA) from the Food and Drug Administration (FDA) for use in helping to minimize the risk of serious infection with the SARS-CoV-2 virus in people ages 12 years and older.

The active ingredient in Novavax is NVX-CoV2373. The vaccine comes as a liquid suspension that’s given as an injection into your upper arm muscle by a healthcare professional.

Keep reading to learn about common, mild, and serious side effects that Novavax can cause. For a general overview of the drug, including details about its uses, see this article.

Some people may experience mild to serious side effects after a Novavax vaccination. Examples of the drug’s commonly reported side effects include:

* To learn more about this side effect, see the “Side effects explained” section.

Mild side effects have been reported with Novavax. These include:

In most cases, these side effects should be temporary. And some may be easily managed. But if you have symptoms that are ongoing or bothersome, talk with your doctor or pharmacist. And do not stop receiving Novavax vaccinations unless your doctor recommends it.

Novavax may cause mild side effects other than those listed above. See the drug’s EUA fact sheet for details.

* To learn more about this side effect, see the “Side effects explained” section.

Serious side effects have been reported with Novavax. These include:

If you develop serious side effects from Novavax, call your doctor right away. If the side effects seem life threatening or you think you’re having a medical emergency, immediately call 911 or your local emergency number.

* To learn more about this side effect, see the “Side effects explained” section.

Note: After the FDA approves a vaccine, it and the Centers for Disease Control and Prevention (CDC) track the side effects. If you’d like to report a side effect you’ve had with Novavax, visit the Vaccine Adverse Event Reporting System (VAERS) website.

Allergic reaction

For some people, Novavax can cause an allergic reaction. If you have a polysorbate 80 allergy, consult your doctor or pharmacist before receiving Novavax.

What might help

If you have mild symptoms of an allergic reaction, such as a mild rash, call your doctor right away. They may suggest a treatment to manage your symptoms and can determine whether you should continue receiving Novavax vaccines.

If you have symptoms of a severe allergic reaction, such as swelling or difficulty breathing, call 911 or your local emergency number right away. These symptoms could be life threatening and require immediate medical care.

If your doctor confirms you’ve had a serious allergic reaction to Novavax, they may have you switch to a different COVID-19 vaccine next time.

Get answers to some frequently asked questions about side effects of Novavax.

Are the side effects of Novavax the same as those of mRNA vaccines?

Comirnaty (Pfizer) and Moderna COVID-19 are mRNA vaccines, whereas Novavax is a protein subunit vaccine. Overall, the majority of side effects for these COVID-19 vaccines are similar.

Side effects of all three COVID-19 vaccines include:

  • injection site reaction
  • fatigue
  • headache
  • muscle pain
  • chills or fever
  • nausea and vomiting
  • myocarditis and pericarditis
  • severe allergic reaction

There have also been rare reports of facial paralysis (Bell’s palsy) with the Comirnaty, Novavax, and Moderna COVID-19 vaccines.

Novavax had other rare side effects reported in its studies, such as:

  • gallbladder inflammation
  • inflammation of the middle layer of the eye

And distinct side effects reported during Moderna’s COVID-19 vaccine studies included:

  • delayed injection site reactions that started more than 7 days after vaccination
  • shingles

If you have questions about which COVID-19 vaccine to choose, check with your doctor or pharmacist. They can help you decide which vaccine is best for you.

How long do Novavax side effects last?

Most side effects from Novavax vaccination are mild and resolve in 7 to 14 days. If you have severe symptoms or symptoms that persist beyond 7 days, contact your doctor right away.

What are the long-term side effects of Novavax?

The long-term side effects from Novavax may result from its serious side effects, such as:

The risk of long-term effects of COVID-19 infection far outweighs the risk of long-term side effects with Novavax vaccination. If you’re concerned about your risk of long-term side effects from Novavax, speak with your doctor or pharmacist.

Learn more about some of the side effects Novavax may cause.

Heart lining or heart muscle inflammation

Heart lining and heart muscle inflammation were rare side effects reported in studies of Novavax. The medical terms for these heart side effects are pericarditis and myocarditis.

Pericarditis and myocarditis may cause symptoms such as:

In younger children, pericarditis and myocarditis may cause symptoms such as:

  • fussiness
  • listlessness
  • lack of appetite
  • rapid breathing
  • vomiting

People with a higher risk of developing pericarditis and myocarditis after receiving this vaccine include:

  • males ages 12 to 39 years
  • people with previous pericarditis and myocarditis after a COVID-19 vaccine
  • people with a history of heart problems

What might help

The CDC suggests that an 8-week interval between the first and second Novavax doses may reduce the small risk of myocarditis and pericarditis. And recognizing symptoms of these heart conditions and promptly seeking medical care if you have them can help prevent long-term damage to the heart.

Another important point to consider is that a COVID-19 infection itself can cause myocarditis and pericarditis, which may be more serious when caused directly by the viral infection.

If you have questions about Novavax and your risk of myocarditis and pericarditis, talk with your doctor or pharmacist.

Injection site reaction

Injection site reactions were a common side effect reported in studies of Novavax. These reactions may cause symptoms such as:

  • a hard lump
  • itching
  • pain or tenderness
  • red, darkened, or bruised skin
  • warmth or swelling

Factors that can increase the risk of an injection site reaction with Novavax include:

  • incorrect position of your arm while receiving the vaccine
  • sensitivity to vaccine ingredients
  • receiving the injection while the vaccine is still cold

What might help

To help lower your chance of injection site reactions from Novavax, consider the following:

  • Tell your doctor or pharmacist about any sensitivities or reactions you’ve had in the past.
  • Completely remove your arm from your sleeve.
  • Relax and make sure your arm is loose and hanging down.
  • Avoid rubbing the injection site after receiving a dose.

It’s important to note that vaccines are created to activate the immune system. This means there’s always a possibility of a reaction at the injection site.

If you develop a reaction at the injection site, the following may help to relieve your symptoms:

  • Move the arm frequently to increase blood circulation.
  • Take over-the-counter (OTC) acetaminophen to reduce pain.
  • Apply a cold compress to reduce swelling.

Blood clots

Blood clots were a rare side effect reported in studies of Novavax. Blood clots may cause conditions such as:

  • pulmonary embolism (blood clot in the lung), with symptoms such as:
  • blood clot in the leg or arm, with symptoms such as:
    • reddish skin discoloration, warmth, and swelling in one limb
    • pain when standing, walking, or moving the limb

Factors that can increase the risk of blood clots after receiving this vaccination include:

  • taking oral contraceptives
  • a sedentary lifestyle or prolonged inactivity
  • smoking
  • a body mass index (BMI) of 30 or greater
  • a history of blood clotting disorders

What might help

It’s important to be aware of blood clot symptoms and obtain immediate medical care if they occur. This will reduce your risk of stroke, heart attack, and life threatening pulmonary embolism.

If you’re at risk of blood clots, be sure to talk with your doctor or pharmacist to determine your best COVID-19 vaccination option.

Keeping track of side effects

After your Novavax vaccination, consider taking notes on any side effects you’re having. You can then share this information with your doctor. This is especially helpful when you receive your first vaccination.

Your side effect notes can include things such as:

  • how soon you had the side effect after receiving the vaccination
  • what your symptoms were
  • how your symptoms affected your daily activities
  • what other medications you were taking
  • any other information you feel is important

Sharing notes with your doctor will help them learn more about how Novavax affects you. They can then use this information to adjust your treatment plan if needed.

Below is important information you should consider before receiving the Novavax vaccine.

Warnings

Novavax can sometimes cause harmful effects in people with certain conditions. This is known as a drug-condition interaction. Other factors may also affect whether Novavax is a good vaccine option for you. Talk with your doctor about your health history before receiving Novavax. Be sure to tell them if any of the following factors apply:

  • you have a history of heart lining or heart muscle inflammation
  • you have a history of a bleeding disorder or you take a blood thinner
  • you have a history of fainting after a vaccine
  • you have a weakened immune system or you take an immune-suppressing medication
  • you take other medications, OTC drugs, herbs, vitamins, or nutritional supplements
  • you’ve received another COVID-19 vaccine
  • you’ve had a previous allergic reaction to Novavax or any of its ingredients, such as polysorbate 80
  • you’re pregnant
  • you’re breastfeeding
  • you consume alcohol

Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.