Novavax Says Its COVID-19 Vaccine Is 90% Effective

Older man receiving a vaccine shot while wearing mask.

Kathrin Ziegler / Getty Images

Key Takeaways

  • Pharmaceutical company Novavax just completed its Phase 3 clinical trial in the U.K.
  • The company says its vaccine is nearly 90% effective at preventing COVID-19.
  • The vaccine was much less effective against the South African strain of the virus.

Pharmaceutical company Novavax recently shared results of its Phase 3 clinical trial in the U.K. and, according to the company, its vaccine is nearly 90% effective at preventing COVID-19.

Novavax revealed in a press release last week that its vaccine prevented nine out of 10 cases of COVID-19 in its clinical trial of 15,000 volunteers in the U.K.

The vaccine was also effective against B.1.1.7, the highly infectious strain of SARS-CoV-2, the virus that causes COVID-19, that has been heavily circulating in the U.K. However, the Novavax vaccine had much lower effectiveness against the South African strain, B.1.351. In a study of 4,400 participants in South Africa, the vaccine was only 49% effective. However, when the data only accounted for participants who did not have HIV, the efficacy increased to 60%.

The Novavax vaccine, aka NVX-CoV2373, “is the first vaccine to demonstrate not only high clinical efficacy against COVID-19 but also significant clinical efficacy against both the rapidly emerging U.K. and South Africa variants,” Stanley C. Erck, president and chief executive officer at Novavax, said in the press release. “NVX-CoV2373 has the potential to play an important role in solving this global public health crisis. We look forward to continuing to work with our partners, collaborators, investigators and regulators around the world to make the vaccine available as quickly as possible.”

The Novavax vaccine is currently in Phase 3 clinical trials in the U.S.

What This Means For You

The Novavax COVID-19 vaccine has a high efficacy rate overall. It's currently in Phase 3 clinical trials in the U.S. and is currently not authorized for use in America. If it is approved, it could be another vaccine available to help reduce the spread of COVID-19.

How the Novavax Vaccine Works

The Novavax vaccine works differently than the two vaccines currently approved for use in the U.S. Those vaccines, made by Pfizer-BioNTech and Moderna, use a newer form of technology known as messenger RNA (mRNA). Those vaccines encode a part of the spike protein that's found on the surface of SARS-CoV-2. The mRNA vaccines use pieces of the encoded protein to create an immune response from your body. As a result, you develop antibodies to the virus.

The Novavax vaccine “uses an insect cell line,” infectious disease expert Amesh A. Adalja, MD, senior scholar at the Johns Hopkins Center for Health Security in Maryland, tells Verywell. The cells were infected with a different kind of virus, called a baculovirus, and created spike proteins similar to the spikes on the surface of SARS-CoV-2, he explains. 

The vaccine contains several spike nanoparticles, which attract immune cells. Those immune cells create antibodies to the spike protein that can help prevent future COVID-19 infections. “It’s innovative,” Adalja says.

The way the Novavax vaccine works is “not that different from our influenza vaccine—the parts are just slightly different,” Thomas Russo, MD, professor and chief of infectious disease at the University at Buffalo in New York, tells Verywell.

The Novavax vaccine is stable at normal refrigerator temperatures, making it easier to store and administer than the currently approved vaccines—a big plus for distribution, according to Adalja.

Novavax Vaccine Safety Information

Novavax hasn’t yet released safety information on its vaccine or given details about side effects. The company said in its press release that the vaccine cannot cause COVID-19 and cannot replicate inside the body.

Novavax has not given details yet about potential side effects, but said that its safety database showed that “severe, serious, and medically attended adverse events occurred at low levels and were balanced between vaccine and placebo groups.”

More Research Needed

While preliminary data sounds promising, Stanley Weiss, MD, professor at the Rutgers New Jersey Medical School and the Department of Epidemiology at the Rutgers School of Public Health, stresses that there’s not a lot of information available about the vaccine at this point.

“They have not even published preprint data,” he says. “The scrutiny that the data needs to undergo hasn’t been done by me or the scientific community.”

Weiss says the lower efficacy against the South African strain of the virus is “concerning,” adding, “we need more details about that, including details about whether the vaccine performs better in younger or older people.”

Russo says he’s “not in love with” the vaccine’s efficacy against the South African strain of the virus, but is eager to learn more about the vaccine.

But, overall, Adalja says, the vaccine is “still highly effective at preventing severe disease with COVID-19—that’s what matters.” The end goal, he says, is “to turn COVID-19 into a cold. If we can get several effective vaccines, we can hopefully get there.”

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.

3 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Novavax. Novavax COVID-19 vaccine demonstrates 89.3% efficacy in UK phase 3 trial. Updated January 28, 2021.

  2. The New York Times. Coronavirus vaccine tracker. Updated January 31, 2021.

  3. Centers for Disease Control and Prevention. Understanding mRNA COVID-19 vaccines. Updated December 18, 2020.

By Korin Miller
Korin Miller is a health and lifestyle journalist who has been published in The Washington Post, Prevention, SELF, Women's Health, The Bump, and Yahoo, among other outlets.