Novavax COVID-19 Vaccine Shows Efficacy Against South African, United Kingdom Variants

Novavax announced today its investigational COVID-19 vaccine, NVX–CoV2373, has shown varying efficacy against both the United Kingdom and South African variants.

In the UK-based trial the vaccine showed 86.3% efficacy, and in the South African trial it demonstrated an overall efficacy of 48.6% against predominantly variant strains, and with HIV-negative participants, 55.4% efficacy was observed.

In both studies the vaccine demonstrated 100% protection against severe disease, including all hospitalization and death. And analyses from both trials showed that the vaccine is well-tolerated, with low levels of severe, serious and medically attended adverse events at day 35, balanced between vaccine and placebo groups.

"We are very encouraged by the data showing that NVX-CoV2373 not only provided complete protection against the most severe forms of disease, but also dramatically reduced mild and moderate disease across both trials. Importantly, both studies confirmed efficacy against the variant strains," Novavax President and Chief Executive Officer Stanley C. Erck, said.

UK Trial
The study enrolled more than 15,000 participants between 18-84 years of age, including 27% over the age of 65. The primary endpoint of this phase 3 clinical trial was based on the first occurrence of PCR-confirmed symptomatic (mild, moderate or severe) COVID-19 with onset at least 7 days after the second study vaccination in serologically negative (to SARS-CoV-2) adult participants at baseline.

In volunteers 65 years of age and older, 10 cases of COVID-19 were observed, with 90% of those cases occurring in the placebo group.

South Africa Trial
This trial was a randomized, observer-blinded, placebo-controlled phase 2b clinical trial of NVX-CoV2373. One cohort evaluated efficacy, safety, and immunogenicity in approximately 2665 healthy adults. The second cohort evaluated safety and immunogenicity in approximately 240 medically stable, HIV-positive adults.

A previously reported initial analysis from the study through 60 days indicated that prior infection with the original COVID-19 strain might not completely protect against subsequent infection by the variant predominantly circulating in South Africa.

However, the complete analysis of the South Africa trial indicates that there may be a late protective effect of prior exposure with the original COVID-19 strain. In placebo recipients, at 90 days the illness rate was 7.9% in baseline seronegative individuals, with a rate of 4.4% in baseline seropositive participants.

The company is using its saponin-based Matrix-M adjuvant platform. It has shown a potent and well-tolerated effect by stimulating the entry of antigen presenting cells into the injection site and enhancing antigen presentation in local lymph nodes, boosting immune response.

The company has not offered any insights for a timeline for filing an Emergency Use Authorization with the Food and Drug Administration.