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Randomized Controlled Trial
. 2024 Jul 19;79(1):78-85.
doi: 10.1093/cid/ciae081.

Durability of Protection Against COVID-19 Through the Delta Surge for the NVX-CoV2373 Vaccine

Dean Follmann  1 , Allyson Mateja  2 , Michael P Fay  1 , Craig A Magaret  3 , Yunda Huang  3 , Youyi Fong  3 , Heather Angier  3 , Martha Nason  1 , Cynthia L Gay  4 , Karen Kotloff  5 , Wayne Woo  6 , Iksung Cho  6 , Lisa M Dunkle  6
Affiliations
Randomized Controlled Trial

Durability of Protection Against COVID-19 Through the Delta Surge for the NVX-CoV2373 Vaccine

Dean Follmann et al. Clin Infect Dis. .

Abstract

Background: Protein-based vaccines for coronavirus disease 2019 (COVID-19) provide a traditional vaccine platform with long-lasting protection for non-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pathogens and may complement messenger RNA vaccines as a booster dose. While NVX-CoV2373 showed substantial early efficacy, the durability of protection has not been delineated.

Methods: The PREVENT-19 vaccine trial used a blinded crossover design; the original placebo arm received NVX-CoV2373 after efficacy was established. Using novel statistical methods that integrate surveillance data of circulating strains with post-crossover cases, we estimated placebo-controlled vaccine efficacy and durability of NVX-CoV2373 against both pre-Delta and Delta strains of SARS-CoV-2.

Results: Vaccine efficacy against pre-Delta strains of COVID-19 was 89% (95% CI, 75-95%) and 87% (72-94%) at 0 and 90 days after 2 doses of NVX-CoV2373, respectively, with no evidence of waning (P = .93). Vaccine efficacy against the Delta strain was 88% (71-95%), 82% (56-92%), and 77% (44-90%) at 40, 120, and 180 days, respectively, with evidence of waning (P < .01). In sensitivity analyses, the estimated Delta vaccine efficacy at 120 days ranged from 66% (15-86%) to 89% (74-95%) per various assumptions of the surveillance data.

Conclusions: NVX-CoV2373 has high initial efficacy against pre-Delta and Delta strains of COVID-19 with little evidence of waning for pre-Delta strains through 90 days and moderate waning against Delta strains over 180 days.

Keywords: COVID-19; NVX-CoV2373; SARS-CoV-2; vaccine durability.

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Conflict of interest statement

Potential conflicts of interest. M. P. F. reports support for meetings and/or travel from NIAID. A. M. received funds from the National Cancer Institute. C. A. M. received funds to their institution from the National Institutes of Health Coronavirus Prevention Network. Y. H., H. A., and K. K. received funds to their institution from NIAID. Y. H. received funds to their institution from the World Health Organization. K. K. also received funds to their institution for Novavax: A 2-Part Phase 2/3 Open-Label Study to Evaluate the Safety and Immunogenicity of a XBB.1.5 (Omicron Subvariant) SARS-CoV-2 rS Vaccine Booster Dose in Previously mRNA COVID-19 Vaccinated and Baseline SARS-CoV-2 Seropositive COVID-19 Vaccine Naïve Participants and has leadership as the National Co-Chair Novavax Phase 3 Trials of NIAID. L. M. D., W. W., and I. C. are employees and stockholders of Novavax, Inc. All other authors report no potential conflicts. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed.

Figures

Figure 1.
Figure 1.
Cumulative incidence of pre-crossover dropout and crossover initiation through the end of the crossover period, 24 July 2021. N = 25 519.
Figure 2.
Figure 2.
Cumulative incidence of the first instance of COVID-19 along with circles denoting the timing of COVID-19 cases annotated by strain and vaccination status (ie, received both doses of NVX-CoV2373). Both sequenced and imputed strains are included. Note the NVX-COV2373:placebo randomization ratio was 2:1. Abbreviation: COVID-19, coronavirus disease 2019.
Figure 3.
Figure 3.
Placebo-controlled vaccine efficacy against pre-Delta COVID-19 as a function of days since full immunization. A bend-point is specified at 75 days. Circles denote the time of COVID-19 cases on the x-axis annotated by vaccination status. Time is relative to the second injection of the pre-crossover dosing for placebo unvaccinated cases and NVX-CoV2373 cases and relative to the post-crossover second dose for placebo vaccinated cases. Abbreviations: CI, confidence interval; COVID-19, coronavirus disease 2019.
Figure 4.
Figure 4.
Counterfactual placebo-controlled vaccine efficacy against Delta COVID-19 as a function of days since full immunization. The vaccine efficacy curve starts at 40 days post–full immunization to avoid extrapolation. A bend-point is specified at 140 days. Circles denote the time of COVID-19 cases on the x-axis annotated by vaccination status. Time is relative to the second injection of the pre-crossover dosing for placebo unvaccinated cases and NVX-CoV2373 cases and relative to the post-crossover second dose for placebo vaccinated cases. Abbreviations: CI, confidence interval; COVID-19, coronavirus disease 2019.
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