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Novavax's COVID-19 shots are 90% effective, company reports

silouette of hands prepping a syringe for injection in front of white background with word "Novavax" written across it in blue
(Image credit: Getty/SOPA Images/Contributor)

The COVID-19 vaccine produced by Novavax showed an overall efficacy of 90% in a late-stage clinical trial, meaning the shot appears roughly as protective as those made by Pfizer-BioNTech and Moderna, the company announced Monday (June 14). 

The trial began in December 2020 after several concerning coronavirus variants had already become widespread, including the Alpha variant discovered in the U.K. and Beta variant found in South Africa. In contrast, the Pfizer-BioNTech and Moderna trials took place before these variants emerged. 

The Novavax trial included 29,960 participants across 119 sites in the U.S. and Mexico, according to a statement from the company. Half of the participants received the vaccine, while the other half got a placebo shot. A total of 77 cases of COVID-19 cropped up during the trial: 63 in the placebo group and 14 in the vaccine group. All cases in the vaccinated group turned out to be mild, while 10 moderate cases and four severe cases were observed in the placebo group.

On a call with investors, Novavax representatives noted that six additional people in the placebo group required hospitalization during the trial, and one of these individuals died, STAT News reported. However, the positive COVID-19 test results for these individuals were not confirmed at the trial's central laboratory, so they were not included in the efficacy analysis. 

Related: 20 of the worst epidemics and pandemics in history 

Based on the data provided so far, the Novavax vaccine appears 100% effective against moderate and severe COVID-19 infections and 90.4% effective against symptomatic infections, the company reported. And specifically, the vaccine was 91% effective at protecting against symptomatic infection among high-risk individuals — meaning those with existing medical conditions that increase the risk of severe infection, those at high risk of exposure and those older than age 65.

"It's a strong result," Natalie Dean, a biostatistician at the University of Florida, told The New York Times. "It puts them up in that high tier."

The company has yet to release the full trial data and plans to do so at a future date. "Further analyses of the trial are ongoing and will be shared via preprint servers as well as submitted to peer-review journals for publication," the company statement notes.

In its Monday press release, Novavax also reported that the vaccine is 93% protective against "variants of concern" (VOC) and "variants of interest" (VOI). VOCs are defined as versions of the virus with increased transmissibility, disease severity or ability to thwart vaccines or treatments, according to the Centers for Disease Control and Prevention (CDC); VOIs carry genetic differences that could cause changes in transmissibility and disease severity, but the mutants still show limited prevalence.

The company looked for VOCs and VOIs by analyzing the genetic material of the virus in 54 of the 77 COVID-19 cases. Of the 77 cases, 35 involved VOCs and nine involved VOIs; 38 of these 44 VOC and VOI cases occurred in the placebo group, with six in the vaccinated group. 

About half of the participants infected with a VOC were infected with the Alpha variant, also known as B.1.1.7, STAT News reported. Few caught the Beta or Gamma variants, first discovered in South Africa and Brazil, respectively, and none caught the Delta variant, identified in India, so the vaccine's potency against Delta remains unknown.

"All of these more resistant variants are going to cause a degree of loss of potency," John Moore, an immunologist at Weill Cornell University and participant in the trial, told STAT. "But with these strong vaccines, it's not going to be wipe-outs."

Novavax will apply for emergency use authorization (EUA) in the U.S. after completing a quality control test, to prove that the shots can be reliably produced on large scales, The New York Times reported. The company also plans to apply for authorization in Britain, the European Union, India and South Korea, and will likely receive authorization in one of these countries before it happens in the U.S., Novavax's chief executive Stanley Erck said in an interview.

Whenever the company does apply for U.S. authorization, the Food and Drug Administration may instead require Novavax to apply for full approval, given that three other COVID-19 vaccines are already authorized in the country, the Times reported. 

"The law says that once you have sufficient doses, there's no need for additional EUA's," Dr. Luciana Borio, who was the acting chief scientist at the FDA from 2015 to 2017, told the Times. Once approved, the shots "may be really the right ones for boosters," Borio added.

The vaccine, called NVX-CoV2373, contains nanoparticles studded with modified spike proteins — proteins that stick off the coronavirus and plug into cells to trigger infection, Live Science previously reported. The nanoparticles cannot replicate like a virus or cause COVID-19, but they instead train the immune system to recognize SARS-CoV-2, the virus that causes COVID-19, should the vaccinated person ever become exposed.

The vaccine also contains saponins,  compounds extracted from the soapbark tree that act as an adjuvant, meaning it summons extra immune cells to the vaccination site, the Times reported. The shots can be stored at fridge temperatures and are given in two doses, three weeks apart, according to STAT.

Read more about the recent trial results in STAT News and The New York Times.

Originally published on Live Science.

Nicoletta Lanese

Nicoletta Lanese is a staff writer for Live Science covering health and medicine, along with an assortment of biology, animal, environment and climate stories. She holds degrees in neuroscience and dance from the University of Florida and a graduate certificate in science communication from the University of California, Santa Cruz. Follow Nicoletta on Twitter @NicolettaML.