Novavax Says COVID-19 Vaccine Showed High Efficacy in Phase 3 Trial of Adults

The experimental COVID-19 vaccine, NVX-CoV2373, was found to be highly effective against moderate and severe disease and circulating SARS-CoV-2 variants.

The biotechnology company Novavax announced today, June 14, 2021, that its recombinant nanoparticle protein-based COVID-19 vaccine was approximately 90% effective overall and 100% effective against moderate and severe disease during a phase 3 clinical trial.

The experimental vaccine, dubbed NVX-CoV2373, was also found to be highly effective against SARS-CoV-2 variants of concern and among high-risk populations, according to the manufacturer’s press release.

PREVENT-19 (PRE-fusion protein subunit Vaccine Efficacy Novavax Trial/COVID-19), was a placebo-controlled, observer-blinded phase 3 trial that enrolled 29 960 adults across 119 sites in the US and Mexico from January 25 to April 30, 2021.

The press release added that when recruiting participants, researchers particularly focused on communities and demographic groups most impacted by COVID-19: 13% of participants were aged ≥65 years, 20% Latin American, 12% African American, 7% Native American, and 5% Asian American.

Participants were randomized 2:1 to receive 2 doses of NVX-CoV2373 or placebo. The primary endpoint was the development of PCR-positive, symptomatic mild, moderate, or severe COVID-19 illness diagnosed 7 days after the second vaccine dose.

Overall, NVX-CoV2373 was 90.4% effective (95% confidence interval [CI]: 82.9-94.6), with 77 cases of laboratory-confirmed SARS-CoV-2: 63 in the placebo group and 14 in the vaccine group. All cases in the vaccine group were defined as “mild” by the trial protocol, according to the press release.

Though there were only mild cases of COVID-19 observed in the vaccine group, there were 10 moderate cases and 4 severe cases in the placebo group, yielding a vaccine efficacy of 100% (95% CI: 87-100) against moderate or severe disease.

NVX-CoV2373 was also effective among “high-risk” populations, defined as adults aged ≥65 years with “certain comorbidities” or “life circumstances with frequent COVID-19 exposure,” the press release stated. There were 62 COVID-19 cases in the placebo group and 13 in the vaccine group, yielding a vaccine efficacy of 91.0% (95% CI: 83.6-95) in this population.

NVX-CoV2373 was found to be 93.2% (95% CI: 83.9-97.1) effective against what the Centers for Disease Control and Prevention has defined as variants of concern or variants of interest, including the predominant variant in the US, B.1.1.7, first identified in the United Kingdom.

"PREVENT-19 confirms that NVX-CoV2373 offers a reassuring tolerability and safety profile," Gregory M. Glenn, MD, president of research and development at Novavax, said in the press release. "These data show consistent, high levels of efficacy and reaffirm the ability of the vaccine to prevent COVID-19 amid ongoing genetic evolution of the virus.”

Preliminary safety data showed NVX-CoV2373 was generally well-tolerated, with serious and severe adverse events comparable between cohorts and no single adverse event reported by >1% of participants.

Novavax said it plans to submit these results to a peer-reviewed publication and has applied for emergency use authorization from the Food and Drug Administration. The placebo-controlled portion of PREVENT-19 among adolescents aged 12-17 years is ongoing.