The published data provide additional detail of an initial analysis conducted in January, while more robust data from a complete analysis of the study was subsequently shared in March 2021.
Publication of initial primary analysis in the New England Journal of Medicine (NEJM) highlights cross-protection by the Novavax COVID-19 vaccine against the B.1.351 variant prevalent in South Africa during the study.
This is the first published study to show protection against mild COVID-19 caused by the B.1.351 variant circulating in South Africa.
An updated analysis of the study indicated 100 percent protection against severe COVID-19 due to the B.1.351 variant.
"An efficacy of 50 percent is sufficient to meet the World Health Organization criteria for regulatory approval of the vaccine," says professor of vaccinology Shabir Madhi, director of the Wits Vaccines & Infectious Diseases Analytics (VIDA) research unit.
The Novavax COVID-19 vaccine, known as NVX-CoV2373, is made by Novavax, Inc., a US-based biotechnology company developing next-generation vaccines for serious infectious diseases.
Gregory M. Glenn, MD, president of research and development, Novavax, says: "This data publication reinforces the encouraging safety profile and cross-protective effect across variants seen in studies of our vaccine to-date."
About the study
The Phase 2b randomized, observer-blinded, placebo-controlled trial conducted in South Africa evaluated efficacy, safety and immunogenicity in healthy adults, and in a small cohort of medically stable adults living with human immunodeficiency virus (HIV).
The study met its primary endpoint—i.e., the Novavax vaccine demonstrated an overall efficacy of 49 percent in the initial analysis, and 49 percent in the subsequent complete analysis (unpublished).
Among healthy adults without HIV, the Novavax vaccine demonstrated efficacy of 60 percent in the initial analysis, and 55 percent in the subsequent complete analysis.
In the initial analysis, cases were predominantly mild-to-moderate and due to the B.1.351 variant that dominates in South Africa, and increasingly in southern Africa.
In the subsequent complete analysis, circulation of the B.1.351 variant continued to dominate, and all five cases of severe disease observed in the trial occurred in the placebo group.
The initial analysis, now published in NEJM, suggested that prior infection with the original COVID-19 strain did not protect against subsequent infection by the variant predominantly circulating in South Africa through 60 days of follow-up.
However, with additional follow-up, the complete analysis of the South Africa trial indicates that there may be a modest protective effect of prior exposure with the original COVID-19 strain.
Among placebo recipients, at 90 days of follow-up, the illness rate was 8.0 percent in baseline seronegative participants and 5.9 percent in baseline seropositive participants.
"The data make a compelling case for use of the Novavax COVID-19 vaccine in settings where the B.1.351 variant dominates—which is most of southern Africa—to reduce the risk of mild disease and also to maximize the opportunity for protection against severe COVID," says Madhi. "Further work is required for Novavax and all other COVID-19 vaccines, particularly in people living with HIV."
The Novavax COVID-19 vaccine trial is one of two COVID-19 vaccine trials in South Africa led by Madhi and Wits VIDA, with the other being the Oxford/AstraZeneca COVID-19 vaccine trial.
In addition to directing Wits VIDA, Madhi is dean of the faculty of health sciences at the University of the Witwatersrand, Johannesburg (Wits), and codirector of African Leadership in Vaccinology Expertise (ALIVE).
- This press release was originally published on the University of the Witwatersrand, Johannesburg (Wits) website