Safety and Efficacy of the NVX-CoV2373 Coronavirus Disease 2019 Vaccine at Completion of the Placebo-Controlled Phase of a Randomized Controlled Trial

Paul T Heath, Eva P Galiza, David Neil Baxter, Marta Boffito, Duncan Browne, Fiona Burns, David R Chadwick, Rebecca Clark, Catherine A Cosgrove, James Galloway, Anna L Goodman, Amardeep Heer, Andrew Higham, Shalini Iyengar, Christopher Jeanes, Philip A Kalra, Christina Kyriakidou, Judy M Bradley, Chigomezgo Munthali, Angela M MinassianFiona McGill, 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 L Soiza, Pauline A Swift, Emma C Thomson, Jeremy Turner, Marianne Elizabeth Viljoen, Louis Fries, Iksung Cho, Irene McKnight, Greg Glenn, E Joy Rivers, Andreana Robertson, Katia Alves, Kathy Smith, Seth Toback

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)
2 Downloads (Pure)


BACKGROUND: The recombinant protein-based vaccine, NVX-CoV2373, demonstrated 89.7% efficacy against COVID-19 in a phase 3, randomized, observer-blinded, placebo-controlled trial in the United Kingdom. The protocol was amended to include a blinded crossover; data to the end of the placebo-controlled phase are reported.

METHODS: Adults aged 18-84 years received two doses of NVX-CoV2373 or placebo (1:1) and were monitored for virologically confirmed mild, moderate, or severe COVID-19 (onset from 7 days after second vaccination). Participants who seroconverted to immunoglobulin G (IgG) against the nucleocapsid protein and did not meet criteria for symptomatic COVID-19 were classified as having asymptomatic disease. Secondary outcomes included anti-spike (S) IgG responses, wild-type virus neutralization, and T-cell responses.

RESULTS: Of 15185 participants, 13989 remained in the per-protocol efficacy population (6989 NVX-CoV2373, 7000 placebo). At a maximum of 7.5 months (median, 4.5 months) postvaccination, there were 24 cases of COVID-19 among NVX-CoV2373 recipients and 134 cases among placebo recipients, a vaccine efficacy of 82.7% (95% CI: 73.3-88.8). Vaccine efficacy was 100% (17.9-100.0) against severe disease and 76.3% (57.4-86.8) against asymptomatic disease. High anti-S and neutralization responses to vaccination were evident, together with S-protein-specific induction of interferon-γ secretion in peripheral blood T cells. Incidence of serious adverse events and adverse events of special interest were similar between groups.

CONCLUSIONS: A two-dose regimen of NVX-CoV2373 conferred a high level of ongoing protection against asymptomatic, symptomatic, and severe COVID-19 through >6 months postvaccination. A gradual decrease of protection suggests that a booster dose may be indicated.

Original languageEnglish
Pages (from-to)398-407
Number of pages10
JournalClinical Infectious Diseases
Issue number3
Early online date10 Oct 2022
Publication statusPublished - 1 Feb 2023


  • CoVID-19
  • Immunogenicity
  • Asymptomatic Infections
  • SARS-CoV-2
  • Vaccine efficacy


Dive into the research topics of 'Safety and Efficacy of the NVX-CoV2373 Coronavirus Disease 2019 Vaccine at Completion of the Placebo-Controlled Phase of a Randomized Controlled Trial'. Together they form a unique fingerprint.

Cite this