Novavax's COVID-19 Vaccine: Your Questions Answered

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

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 the fourth vaccine authorized by the Food and Drug Administration (FDA) in the U.S. for the prevention of COVID-19 and another tool in an expanding armamentarium. It’s unique among the available coronavirus vaccines in this country in that it uses a traditional virus-blocking technology (one that’s been used against other diseases).

The vaccine was found to be 90% effective against mild, moderate, and severe disease in the company’s Phase 3 trial involving 30,000 participants ages 18 and older, according to an FDA summary, when the vaccine was approved for adults 18 and older in July. In August, authorization for the vaccine was expanded to include adolescents ages 12 to 17, based on data from Novavax’s ongoing pediatric trial. It’s important to note that, for both age groups, the data on the vaccine’s efficacy was gathered before Omicron became the predominant variant, so its efficacy against Omicron and its subvariants is unknown.

Then, in October, the FDA authorized a booster for adults only, although it may not prevent infection by the most recent variants. While the mRNA bivalent boosters from Pfizer and Moderna target both the original strain of the coronavirus and Omicron BA.4 and BA.5 subvariants, the Novavax booster only targets the original SARS-CoV-2 virus. Novavax says it expects to have an updated shot in 2023 but says its booster does provide protection against several strains, including BA.5. 

“It’s good news for many reasons,” says F. Perry Wilson, MD, a Yale Medicine nephrologist and epidemiologist. 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 explains. Even though 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.

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.

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. 

Novavax applied to the FDA for authorization in January of this year.

Anyone 12 or older can get the Novavax vaccine. It’s a two-dose primary series, with the second shot given three to eight weeks after the first. 

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. 

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

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.”

The Novavax clinical trial was conducted before the Omicron variant was circulating, so data doesn’t show how well the vaccine works against recent subvariants. The company is still testing an updated booster for prevention of infection by newer variants.

“Will Novavax have a longer shelf life in the immune system? We don't know yet,” Dr. Wilson says.

With the mRNA vaccines, “particularly in older people, the duration of immune response seems to fall off after four to six months,” Dr. Wilson says, adding that there is now data to show this is the case with Omicron. 

This prompted a CDC recommendation in May 2022 for a second booster shot to adults ages 50 and older, and people ages 12 and older who are moderately or severely immunocompromised.

The Novavax booster targets the original SARS CoV-2 virus and may not protect against infection by Omicron’s recent subvariants. The shot is given six months after the primary vaccine to adults only if they have not received any booster shot previously, and they cannot receive a Pfizer-BioNTech or Moderna mRNA bivalent booster for a medical or any other reason. Teenagers ages 12 through 17 who had the Novavax primary series must get a Pfizer-BioNTech bivalent booster.

As with other COVID-19 vaccines, breakthrough cases, in which someone who is vaccinated still gets infected with COVID-19, 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.”

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.