Novavax’s coronavirus disease 2019 (COVID-19) vaccine candidate, NVX-CoV2373, was found to be 89.3% effective against the disease, according to interim analysis of a phase 3 study conducted in the United Kingdom (UK). 

NVX-CoV2373 is engineered from the genetic sequence of severe acute respiratory syndrome coronavirus 2 (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. It is stable at refrigerated temperatures and is supplied as a ready-to-use liquid formulation.

The randomized, observer-blinded, placebo-controlled trial assessed the efficacy and safety of NVX-CoV2373 in approximately 15,000 adults aged 18 to 84 years, including 27% over the age of 65. Participants were randomly assigned to receive 2 intramuscular injections of either NVX-CoV2373 or placebo administered 21 days apart. The primary end point was prevention of symptomatic COVID-19 disease (7 or more days after the second vaccination).

Interim results showed that NVX-CoV2373 demonstrated vaccine efficacy of 89.3% (95% CI, 75.2-95.4), with 6 cases of COVID-19 observed in the vaccine arm compared with 56 cases in the placebo arm; the UK variant (B.1.1.7) was found in 32 of the 62 cases. A post hoc analysis showed that efficacy by strain was 95.6% against the original COVID-19 variant and 85.6% against the B.1.1.7 variant.

The Company also announced results from a phase 2b trial evaluating NVX-CoV2373 for the prevention of COVID-19 in 4400 adults in the republic of South Africa. In the overall population (HIV-positive and HIV-negative participants), findings showed that the vaccine was 49.4% (95% CI, 6.1-72.8) effective; 92.6% (25/27) of cases were attributed to the B.1.351 variant. Among HIV-negative participants (94%), the vaccine was 60% effective (95% CI, 19.9-80.1) at preventing mild, moderate and severe disease.

“With today’s results from our UK phase 3 and South Africa phase 2b clinical trials, we have now reported data on our COVID-19 vaccine from phase 1, 2 and 3 trials involving over 20,000 participants,” said Stanley C. Erck, President and CEO, Novavax. “NVX-CoV2373 is the first vaccine to demonstrate not only high clinical efficacy against COVID-19 but also significant clinical efficacy against both the rapidly emerging UK and South Africa variants.”

The Company is also investigating NVX-CoV2373 in another phase 3 trial (PREVENT-19) being conducted in the US and Mexico.


Novavax COVID-19 vaccine demonstrates 89.3% efficacy in UK phase 3 trial. [press release]. Gaithersburg, MD: Novavax, Inc; January 28, 2021.