Novavax COVID-19 Vaccine Demonstrates 90% Overall Efficacy


Novavax’s recombinant nanoparticle protein-based COVID-19 vaccine showed an overall efficacy of 90.4% and 100% efficacy against moderate and severe disease.

Novavax COVID-19 vaccine

Novavax’s recombinant nanoparticle protein-based COVID-19 vaccine showed an overall efficacy of 90.4%, according to the results of a phase 3 study. 

The investigational NVX-CoV2373 met the primary end point in its PREVENT-19 phase 3 trial, which enrolled 29,960 participants across the United States and Mexico. Additional key findings showed 100% protection against moderate and severe COVID-19. Novavax plans to file for regulatory authorizations in the third quarter of 2021.

In the PREVENT-19 trial, a total of 77 COVID-19 cases were observed: 63 in the placebo group and 14 in the vaccine group. All cases observed in the vaccine group were mild, and 10 moderate cases and 4 severe cases occurred in the placebo group. The primary end point for PREVENT-19 was the first occurrence of polymerase chain reaction (PCR) confirmed symptomatic COVID-19 with onset at least 7 days after the second dose in serologically negative adult participants at baseline.

According to Novavax, the efficacy end points were accrued from January 25 through April 30, 2021, when the Alpha (B.1.1.7) variant became the predominant strain in the United States, and other strains such as variants of interest (VoI) and variants of concern (VoC) were on the rise. Against VoC/VoI, which represented 82% of the cases, vaccine efficacy was 93.2% (95% CI: 83.9, 97.1), according to the results. NVX-CoV2373 also demonstrated efficacy among high-risk populations, defined as those over age 65, under age 65 with certain comorbidities, or having life circumstances with frequent COVID-19 exposure. Vaccine efficacy among this group was 91.0% (95% CI: 83.6, 95.0), with 62 COVID-19 cases in the placebo group and 13 COVID-19 cases in the vaccine group.

Regarding safety, preliminary data from the study showed the vaccine to be generally well tolerated. No single adverse effect (AE) was reported by more than 1% of participants. Injection site pain and tenderness, generally mild to moderate in severity, were the most common local reactions, lasting less than 3 days. Fatigue, headache, and muscle pain were the most common systemic symptoms, which generally lasted less than 2 days.

“PREVENT-19 confirms that NVX-CoV2373 offers a reassuring tolerability and safety profile,” said Gregory M. Glenn, MD, president of research and development, Novavax. “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. Our vaccine will be a critical part of the solution to COVID-19 and we are grateful to the study participants and trial staff who made this study possible, as well as our supporters, including the US government.”

A placebo-controlled portion of PREVENT-19 is ongoing in adolescents 12 to less than 18 years of age.


  1. Novavax COVID-19 Vaccine Demonstrates 90% Overall Efficacy and 100% Protection Against Moderate and Severe Disease in PREVENT-19 Phase 3 Trial. News Release. Novavax; June 14, 2021. Accessed June 15, 2021.

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