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Novavax's COVID-19 Vaccine: Your Questions Answered

BY KATHY KATELLA October 20, 2022

The only non-mRNA vaccine available in the U.S. is now updated to protect against currently circulating Omicron variants.

[Originally published: July 20, 2022. Updated: Oct. 5, 2023.]

Note: Information in this article was accurate at the time of original publication. Because information about COVID-19 changes rapidly, we encourage you to visit the websites of the Centers for Disease Control & Prevention (CDC), World Health Organization (WHO), and your state and local government for the latest information.

The Novavax vaccine is one of three vaccines available in the U.S. for the prevention of COVID-19 and the only one that does not use the relatively new mRNA vaccine technology. It’s unique among the available coronavirus vaccines here in that it uses a traditional virus-blocking technology that’s been used against other diseases.

The FDA approved a 2023-2024 Novavax vaccine in October 2023 for ages 12 and older to target the SARS-CoV-2 XBB.1.5 strain a few weeks after newly updated Pfizer-BioNTech and Moderna mRNA vaccines were approved. Novavax’s version replaces its original vaccine, which was found to be 90% effective in its initial clinical trials.

“It’s good news for many reasons,” said F. Perry Wilson, MD, a Yale Medicine nephrologist and epidemiologist, when the original Novavax vaccine was authorized. One is that this is an additional vaccine choice that may be acceptable to some of the more than 30% of Americans who are not fully vaccinated, he explained. Even though the Pfizer-BioNTech and Moderna mRNA vaccines are safe and highly effective, “we’ve heard a lot of people say the reason they've chosen not to get an mRNA vaccine is because the mRNA technology is relatively new and it hasn't been tried on a wide scale before.”

There are practical reasons as well. “It’s ideal to have more than one or two companies being the sole providers of vaccines,” Dr. Wilson says. “We know how supply chains can get disrupted, and we want to make sure there's adequate vaccine available. We also want multiple production lines that potentially can be updated to address new variants and meet the challenges as they come.”

Here are some things you should know about the Novavax vaccine.

How is Novavax different than the other COVID-19 vaccines in the U.S.?

Though COVID vaccines may utilize different delivery mechanisms, the end result is the same: cells in the body recognize that a spike protein (the spikes you see sticking out of the coronavirus in pictures) doesn’t belong, and the immune system reacts by activating immune cells and producing antibodies to attack the real virus if you get exposed.

But, unlike the other vaccines, Novavax directly injects a version of the spike protein, along with another ingredient that also stimulates the immune system, into the body, leading to the production of antibodies and T-cells. (It injects a version of the spike protein that has been formulated in a laboratory as a nanoparticulate that does not have genetic material inside and cannot cause disease.) 

“I often tell people, imagine an eggshell without an egg in it. That’s what it is,” Dr. Wilson says.

The Novavax vaccine is a traditional one compared to the other vaccines. Its technology has been used before in vaccines to prevent such conditions as shingles, human papillomavirus, and DTaP (diphtheria, tetanus, and pertussis), among others.

Has the Novavax vaccine been authorized outside of the U.S.?

Yes. The Novavax coronavirus vaccine (brand names: Nuvaxovid and Covovax) is already being used to prevent the coronavirus in 40 other countries, including Canada.

Novavax is based in Maryland, and the vaccine was developed in the U.S. in 2020 with support from the federal government program Operation Warp Speed, but it’s progress was slowed by manufacturing difficulties. Finally, in November 2021, countries around the world, starting with Indonesia and the Philippines, later followed by the United Kingdom, began granting authorizations for the vaccine.

Who can get the Novavax vaccine?

Anyone 12 or older can get the 2023-2024 Novavax vaccine. Anyone who has previously been vaccinated (with any COVID vaccine) may get one dose at least two months after the first dose. Those who have never been vaccinated may get two doses administered three weeks apart.

People who are immunocompromised may get an additional dose at least two months after their last dose of a 2023-2024 COVID vaccine. Additional doses may be administered at the discretion of a health care provider with the timing based on the individual’s clinical circumstances.

What are the side effects of the Novavax COVID-19 vaccine?

The most commonly reported side effects by vaccine recipients in the clinical trial were pain/tenderness, redness and swelling at the injection site, fatigue, muscle pain, headache, joint pain, nausea/vomiting, and fever. There is a remote chance that the vaccine could cause a severe allergic reaction, which would usually occur within a few minutes after the immunization. You should not get the Novavax vaccine if you’ve had a severe allergic reaction to a previous dose of it, or a severe reaction to any of the ingredients in the vaccine.

Approximately 21,000 vaccine recipients had at least two months of safety follow-up after their second dose, according an FDA statement.

Is myocarditis a side effect?

Myocarditis, a rare form of inflammation of the heart muscle, occurred in a handful of Novavax clinical trial participants, all of whom were men. Novavax says “there is insufficient evidence to establish a causal relationship" between the vaccine and the condition. A committee that advised the FDA to authorize the Novavax vaccine decided the benefits of vaccination outweigh the risks of developing heart inflammation. 

But, the Fact Sheet for Recipients and Caregivers says that in most people who have developed myocarditis or pericarditis (inflammation of the outer lining of the heart), symptoms began within 10 days following vaccination. It says vaccine recipients should seek medical attention right away if they experience any of the following symptoms: chest pain, shortness of breath, and/or feelings of having a fast-beating, fluttering, or pounding heart.

Similar rare reports have risen around the mRNA vaccines, and the FDA has issued a warning label on both the Pfizer and Moderna vaccines regarding myocarditis and pericarditis in adolescents and young adults. With the mRNA vaccines, the inflammation, in most cases, gets better on its own without treatment.

“There's some data suggesting that certain proteins in the heart look like spike proteins—but it doesn't look that much like a spike protein, so why certain individuals have more of a reaction than others is still not clear,” says Dr. Wilson. “We know people who have developed this rare condition are more likely to be male. We know they tend to be younger. There may be some genetic factors at play, too, but that's still all up in the air.”

As to whether people should be concerned about the risk, he says, “The risk of myocarditis is higher from COVID than it is from any of the COVID vaccines.”

Is Novavax effective against Omicron and its subvariants?

The FDA authorization for the 2023-2024 Novavax vaccine was based on non-clinical data showing that the shot induced functional immune responses against XBB.1.5 and its subvariants and should induce a broad response against currently circulating variants. That includes EG.5, which in early October accounted for almost 30% of cases, according to the CDC.

Will Novavax prevent breakthrough infections?

As with other COVID vaccines, breakthrough cases, in which someone who is vaccinated still gets infected with COVID, remain a reality.

“You're still going to see transmission of COVID, even among vaccinated people,” Dr. Wilson says. “But importantly, what we’re counting on the vaccines for is to reduce hospitalizations and deaths. That’s where I think the real benefit is going to come from, in reducing the burden on our hospitals and saving more lives over time.”

More information on the 2023-2024 Novavax vaccine is available on the Fact Sheet for Recipients and Caregivers.

Information provided in Yale Medicine articles is for general informational purposes only. No content in the articles should ever be used as a substitute for medical advice from your doctor or other qualified clinician. Always seek the individual advice of your health care provider with any questions you have regarding a medical condition.

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