King's College London

Research portal

Safety and Efficacy of NVX-CoV2373 Covid-19 Vaccine

Research output: Contribution to journalArticlepeer-review

Original languageEnglish
Pages (from-to)1172-1183
Number of pages12
JournalNew England Journal of Medicine
Issue number13
Published23 Sep 2021

Bibliographical note

Funding Information: The trial was designed and funded by Novavax, the manufacturer of NVX-CoV2373. The trial protocol was approved by the North West–Greater Manchester Central Research Ethics Committee. The trial was performed in accordance with the Good Clinical Practice guidelines of the International Council for Harmonisation. (Details regarding trial oversight are provided in the Supplementary Appendix, available at All data were gathered by the non-Novavax authors (representing each trial site) and their teams; all the analyses were performed by representatives of Novavax. Confidentiality agreements were in place between all the authors and the trial sponsor. The first draft of the manuscript was written by the first author with subsequent contributions from all the authors. Editorial assistance in the preparation of the manuscript was provided by Phase Five Communications and funded by No-vavax. All trial data were available to all the authors. Safety oversight for specific rules regarding a pause in vaccination was performed by an independent safety monitoring committee. All the authors assume responsibility for the accuracy and completeness of the data and for the fidelity of the trial to the protocol. Funding Information: Supported by Novavax. Infrastructure support for sites was provided by the NIHR Clinical Research Network. Publisher Copyright: Copyright © 2021 Massachusetts Medical Society. Copyright: Copyright 2021 Elsevier B.V., All rights reserved.

King's Authors


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

View graph of relations

© 2020 King's College London | Strand | London WC2R 2LS | England | United Kingdom | Tel +44 (0)20 7836 5454