Efficacy of NVX-CoV2373 Covid-19 Vaccine against the B.1.351 Variant

N Engl J Med. 2021 May 20;384(20):1899-1909. doi: 10.1056/NEJMoa2103055. Epub 2021 May 5.

Abstract

Background: The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants threatens progress toward control of the coronavirus disease 2019 (Covid-19) pandemic. In a phase 1-2 trial involving healthy adults, the NVX-CoV2373 nanoparticle vaccine had an acceptable safety profile and was associated with strong neutralizing-antibody and antigen-specific polyfunctional CD4+ T-cell responses. Evaluation of vaccine efficacy was needed in a setting of ongoing SARS-CoV-2 transmission.

Methods: In this phase 2a-b trial in South Africa, we randomly assigned human immunodeficiency virus (HIV)-negative adults between the ages of 18 and 84 years or medically stable HIV-positive participants between the ages of 18 and 64 years in a 1:1 ratio to receive two doses of either the NVX-CoV2373 vaccine (5 μg of recombinant spike protein with 50 μg of Matrix-M1 adjuvant) or placebo. The primary end points were safety and vaccine efficacy against laboratory-confirmed symptomatic Covid-19 at 7 days or more after the second dose among participants without previous SARS-CoV-2 infection.

Results: Of 6324 participants who underwent screening, 4387 received at least one injection of vaccine or placebo. Approximately 30% of the participants were seropositive for SARS-CoV-2 at baseline. Among 2684 baseline seronegative participants (94% HIV-negative and 6% HIV-positive), predominantly mild-to-moderate Covid-19 developed in 15 participants in the vaccine group and in 29 in the placebo group (vaccine efficacy, 49.4%; 95% confidence interval [CI], 6.1 to 72.8). Vaccine efficacy among HIV-negative participants was 60.1% (95% CI, 19.9 to 80.1). Of 41 sequenced isolates, 38 (92.7%) were the B.1.351 variant. Post hoc vaccine efficacy against B.1.351 was 51.0% (95% CI, -0.6 to 76.2) among the HIV-negative participants. Preliminary local and systemic reactogenicity events were more common in the vaccine group; serious adverse events were rare in both groups.

Conclusions: The NVX-CoV2373 vaccine was efficacious in preventing Covid-19, with higher vaccine efficacy observed among HIV-negative participants. Most infections were caused by the B.1.351 variant. (Funded by Novavax and the Bill and Melinda Gates Foundation; ClinicalTrials.gov number, NCT04533399.).

Publication types

  • Clinical Trial, Phase II
  • Multicenter Study
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Antibodies, Neutralizing / blood
  • COVID-19 / epidemiology
  • COVID-19 / immunology
  • COVID-19 / prevention & control*
  • COVID-19 / virology
  • COVID-19 Serological Testing
  • COVID-19 Vaccines / adverse effects
  • COVID-19 Vaccines / immunology*
  • Double-Blind Method
  • HIV Seronegativity
  • HIV Seropositivity
  • Humans
  • Immunogenicity, Vaccine*
  • Middle Aged
  • SARS-CoV-2* / isolation & purification
  • South Africa
  • Young Adult

Substances

  • Antibodies, Neutralizing
  • COVID-19 Vaccines
  • recombinant SARS-CoV-2 vaccine NVX-cov2373

Supplementary concepts

  • SARS-CoV-2 variants

Associated data

  • ClinicalTrials.gov/NCT04533399