Novavax’s COVID-19 vaccine candidate, NVX-CoV2373, was found to be 100% effective at protecting against moderate and severe disease, according to findings from the phase 3 PREVENT-19 trial. 

NVX-CoV2373 is engineered from the genetic sequence of SARS-CoV-2 using the Company’s recombinant nanoparticle technology to generate antigen derived from the coronavirus spike (S) protein. The vaccine candidate contains the Company’s saponin-based Matrix-M™ adjuvant technology to enhance and prolong immune responses. 

The randomized, placebo-controlled, observer-blinded study ( Identifier: NCT04611802) evaluated the efficacy, safety and immunogenicity of NVX-CoV2373 in 29,960 participants 18 years of age and older in the US and Mexico. Participants were randomly assigned 2:1 to receive 2 intramuscular injections of either NVX-CoV2373 or placebo administered 21 days apart. The primary endpoint was the first occurrence of PCR-confirmed symptomatic COVID-19 with onset at least 7 days after the second dose in serologically negative adult participants at baseline.

Results showed that NVX-CoV2373 met the primary endpoint achieving a vaccine efficacy of 90.4% (95% CI, 82.9-94.6), with 14 cases observed in the vaccine arm compared with 63 in the placebo arm; all cases observed in the vaccine arm were mild. NVX-CoV2373 also achieved a vaccine efficacy of 100% (95% CI, 87-100) against moderate and severe COVID-19, with all cases observed in the placebo arm (10 moderate cases and 4 severe cases).

Sequence data was available for 54 of the 77 cases. NVX-CoV2373 demonstrated 93.2% vaccine efficacy (95% CI, 83.9-97.1) against variants of concern (VoC)/variants of interest (VoI), which represented 44 of the 54 cases, and 100% vaccine efficacy (95% CI, 80.8-100) against variants not considered VoC/VoI. 

Among high-risk populations (defined as 65 years of age and older, or less than 65 years of age with certain comorbidities or having life circumstances with frequent COVID-19 exposure), vaccine efficacy was 91% (95% CI, 83.6-95), with 13 cases observed in the vaccine arm and 62 cases in the placebo arm. 

As for safety, the most common local symptoms were injection site pain and tenderness, which were mild to moderate in severity. The most common systemic symptoms were fatigue, headache and muscle pain.

“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.”

The Company intends to file for regulatory authorizations in the third quarter of 2021.


Novavax COVID-19 vaccine demonstrates 90% overall efficacy and 100% protection against moderate and severe disease in PREVENT-19 phase 3 trial. [press release]. Gaithersburg, MD: Novavax, Inc.; June 14, 2021.