Experts Say Novavax’s COVID-19 Vaccine Shows ‘Very Promising’ Efficacy in Early Research

Korin Miller
·5 min read
Photo credit: Iryna Veklich - Getty Images
Photo credit: Iryna Veklich - Getty Images

From Prevention

There are a lot of COVID-19 vaccines to keep track of lately. So far, the ones from Moderna and Pfizer-BioNTech have been authorized for use in the U.S., but there are plenty of others coming down the pipeline that show promise. One of them is the Novavax vaccine.

In late January, Novavax shared positive results from its phase 3 clinical trials in the U.K. The vaccine development company announced in a press release that its two-dose vaccine is almost 90% effective against preventing symptomatic forms of COVID-19. Worth noting: The vaccine was tested when the highly infectious U.K. variant (B.1.1.7) was widely circulating.

The Novavax vaccine wasn’t highly effective against every coronavirus variant, though. The company announced that its vaccine was 60% effective at preventing mild, moderate, and severe COVID-19 in study participants in South Africa. The reason is likely due to the circulation of the region’s highly infectious variant (B.1.351), says infectious disease expert Amesh A. Adalja, M.D., senior scholar at the Johns Hopkins Center for Health Security.

Recently, Novavax completed enrollment of 30,000 volunteers for its late-stage study in the U.S. and Mexico—a key step toward getting emergency use authorization from the Food and Drug Administration (FDA). Until then, you may be wondering how the Novavax vaccine works and when it might be available. Here’s everything experts know so far.

How does the Novavax COVID-19 vaccine work?

Similar to the Pfizer-BioNTech vaccine, the Novavax vaccine requires two shots given three weeks apart. But that’s where the similarities end, as the Novavax vaccine uses a totally different mechanism to provide protection from COVID-19.

Here’s how it works, per Dr. Adalja: The Novavax vaccine is a protein-based vaccine that’s engineered from the genetic sequence of SARS-CoV-2, the novel coronavirus that causes COVID-19. Its spike protein gene is inserted into an insect virus, called a baculovirus. That virus infects insect cells, which pump out the spike protein. Then, the spike proteins are harvested and combined with an adjuvant, i.e. an ingredient that helps the vaccine create a stronger immune response in your body. “It’s very similar to how the flu vaccine works,” Dr. Adalja notes.

This approach is completely different compared to how the mRNA vaccines work, which give your cells the code to make the spike protein themselves, explains Thomas Russo, M.D., professor and chief of infectious disease at the University at Buffalo in New York. Then, your body develops antibodies in response to these cells. “With the Novavax vaccine, the majority of this process occurs [in a lab] outside your body,” he says. (Important to note: The Novavax vaccine will not cause COVID-19.)

How effective is the Novavax vaccine?

Novavax’s phase 3 clinical trial enrolled more than 15,000 participants between 18 and 84 years old, including 27% who were over the age of 65. The researchers found that, in the U.K. clinical trial, 56 cases of COVID-19 were observed in the placebo group compared to six cases in the vaccinated group. That led to an efficacy rate of 89.3%.

The researchers also discovered that the vaccine was 95.6% effective against the original SARS-CoV-2 strain and 85.6% effective against the U.K. strain. A preliminary analysis discovered that B.1.1.7 (the U.K. strain) was detected in more than 50% of the confirmed symptomatic cases.

The South African phase 2b clinical trial showed that the vaccine was 60% effective at preventing mild, moderate, and severe COVID-19 in study participants who did not have HIV. Overall, there were 29 cases of COVID-19 detected in the placebo group and 15 in the vaccine group.

Novavax points out that about a third of patients enrolled in the South African clinical trial had previously been infected with the original coronavirus strain, while subsequent infections were mostly with the variant virus. “These data suggest that prior infection with COVID-19 may not completely protect against subsequent infection by the South Africa escape variant,” Novavax notes in its press release. “However, vaccination with NVX-CoV2373 provided significant protection.”

“It’s a very promising vaccine,” Dr. Adalja says. “It still prevents severe disease, hospitalization, and death, which means it’s a good vaccine.”

Dr. Russo agrees. “The efficacy is not as high as the mRNA vaccines, but it still affords a reasonable level of protection,” he says. “If we convert a lethal disease into a nuisance and keep people out of the hospital, I think that’s OK.”

Does the Novavax vaccine have side effects?

Novavax hasn’t provided much detail on potential side effects of the vaccine, but for now, they have said this: “Severe, serious, and medically attended adverse events occurred at low levels and were balanced between vaccine and placebo groups.” They note that there were no serious adverse reactions in the trials.

When will the Novavax vaccine be authorized in the U.S.?

It’s not clear at the moment. The vaccine is currently in phase 3 clinical trials in the U.S., so it could still be a while, says William Schaffner, M.D., an infectious disease specialist and professor at the Vanderbilt University School of Medicine.

The New York Times recently reported that, if all goes well, Novavax could have results from the trial by spring, which could mean authorization from the FDA as soon as April. It’s an exciting prospect since, unlike the Pfizer and Moderna vaccines, the Novavax vaccine can be stored and shipped at normal refrigeration temperatures, making distribution much easier.

Ultimately, experts say, we could have a handful of options eventually authorized for use in the U.S. “We probably will have a lot more coronavirus vaccines that appear,” Dr. Adalja confirms.

This article is accurate as of press time. However, as the COVID-19 pandemic rapidly evolves and the scientific community’s understanding of the novel coronavirus develops, some of the information may have changed since it was last updated. While we aim to keep all of our stories up to date, please visit online resources provided by the CDC, WHO, and your local public health department to stay informed on the latest news. Always talk to your doctor for professional medical advice.

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