Background: The recombinant protein-based vaccine, NVX-CoV2373, demonstrated 89.7% efficacy against coronavirus disease 2019 (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 2 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 developed immunoglobulin G (IgG) against nucleocapsid protein but did not show symptomatic COVID-19 were considered asymptomatic. Secondary outcomes included anti-spike (S) IgG responses, wild-type virus neutralization, and T-cell responses. Results: Of 15 185 participants, 13 989 remained in the per-protocol efficacy population (6989 NVX-CoV2373, 7000 placebo). At a maximum of 7.5 months (median, 4.5) 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% confidence interval [CI], 73.3%–88.8%). Vaccine efficacy was 100% (95% CI, 17.9%–100.0%) against severe disease and 76.3% (95% CI, 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 2-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 may be indicated.


© The Author(s) 2022. Published by Oxford University Press on behalf of Infectious Diseases Society of America. This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs licence (https://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reproduction and distribution of the work, in any medium, provided the original work is not altered or transformed in any way, and that the work is properly cited. For commercial re-use, please contact journals.permissions@oup.com

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Heath, P., Galiza, E., Baxter, D., Boffito, M., Browne, D., Burns, F., Chadwick, D., Clark, R., Cosgrove, C., Galloway, J., Goodman, A., Heer, A., Higham, A., Iyengar, S., Jeanes, C., Kalra, P., Kyriakidou, C., Bradley, J., Munthali, C., Minassian, A., McGill, F., Moore, P., Munsoor, I., Nicholls, H., Osanlou, O., Packham, J., Pretswell, C., Francisco Ramos, A., Saralaya, D., Sheridan, R., Smith, R., Soiza, R., Swift, P., Thomson, E., Turner, J., Viljoen, M., Fries, L., Cho, I., McKnight, I., Glenn, G., Rivers, E., Robertson, A., Alves, K., Smith, K. & Toback, S. 2022, 'Safety and efficacy of the NVX-CoV2373 coronavirus disease 2019 vaccine at completion of the placebo-controlled phase of a randomized controlled trial', Clinical Infectious Diseases, 76(3), pp. 398-407. https://doi.org/10.1093/cid/ciac803

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