Safety and Efficacy of the NVX-CoV2373 Covid-19 Vaccine

Paul T Heath, Eva P. Galiza, David Neil Baxter, Marta Boffito, Duncan Browne, Fiona Burns, David R. Chadwick, Rebecca Clarke, Catherine Cosgrove, James N. Galloway, Anna L. Goodman, Andrew Higham, Shalini Iyengar, Arham Jamal, Christopher Jeanes, Philip Kalra, Christina Kyriakidou, Daniel F. McAuley, Agnieszka Meyrick, Angela M. MinassianJane Minton, Patrick Moore, Imrozia Munsoor, Helen Nicholls, Orod Osanlou, Jonathan Packham, Carol H. Pretswell, Alberto San Francisco Ramos, Dinesh Saralaya, Ray P. Sheridan, Richard Smith, Roy Soiza, Pauline A. Swift, Emma C. Thomson, Jeremy Turner, Marianne Elizabeth Viljoen, Gary Albert, Iksung Cho, Filip Dubovsky, Greg Glenn, Joy Rivers, Andreana Robertson, Kathy Smith, Seth Toback* (Corresponding Author), 2019nCoV-302 Study Group

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

581 Citations (Scopus)


Early clinical data from studies of the NVX-CoV2373 vaccine (Novavax), a recombinant nanoparticle vaccine against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that contains the full-length spike glycoprotein of the prototype strain plus Matrix-M adjuvant, showed that the vaccine was safe and associated with a robust immune response in healthy adult participants. Additional data were needed regarding the efficacy, immunogenicity, and safety of this vaccine in a larger population.

In this phase 3, randomized, observer-blinded, placebo-controlled trial conducted at 33 sites in the United Kingdom, we assigned adults between the ages of 18 and 84 years in a 1:1 ratio to receive two intramuscular 5-μg doses of NVX-CoV2373 or placebo administered 21 days apart. The primary efficacy end point was virologically confirmed mild, moderate, or severe SARS-CoV-2 infection with an onset at least 7 days after the second injection in participants who were serologically negative at baseline.

A total of 15,187 participants underwent randomization, and 14,039 were included in the per-protocol efficacy population. Of the participants, 27.9% were 65 years of age or older, and 44.6% had coexisting illnesses. Infections were reported in 10 participants in the vaccine group and in 96 in the placebo group, with a symptom onset of at least 7 days after the second injection, for a vaccine efficacy of 89.7% (95% confidence interval [CI], 80.2 to 94.6). No hospitalizations or deaths were reported among the 10 cases in the vaccine group. Five cases of severe infection were reported, all of which were in the placebo group. A post hoc analysis showed an efficacy of 86.3% (95% CI, 71.3 to 93.5) against the B.1.1.7 (or alpha) variant and 96.4% (95% CI, 73.8 to 99.5) against non-B.1.1.7 variants. Reactogenicity was generally mild and transient. The incidence of serious adverse events was low and similar in the two groups.

A two-dose regimen of the NVX-CoV2373 vaccine administered to adult participants conferred 89.7% protection against SARS-CoV-2 infection and showed high efficacy against the B.1.1.7 variant. (Funded by Novavax; EudraCT number, 2020-004123-16. opens in new tab.)
Original languageEnglish
Pages (from-to)1172-1183
Number of pages12
JournalThe New England Journal of Medicine
Issue number13
Early online date30 Jun 2021
Publication statusPublished - 23 Sept 2021

Bibliographical note

Funded by Novavax, Inc. Infrastructure support for sites was provided by the UK National Institute for Health Research (NIHR) Clinical Research Network EudraCT number, 2020-004123-16.

We are grateful to the UK National Institute for Health Research (NIHR) Clinical Research Network, the NIHR Oxford cognitive health Clinical Research Facility, and the UK Vaccine Task Force.
The views expressed in this publication are those of the author(s) and not necessarily those of the NIHR or the Department of Health and Social Care.

Data Availability Statement

A data sharing statement provided by the authors is available with the full text of this article at


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