As Novavax awaits emergency use authorization (EUA) from the US Food and Drug Administration (FDA) for its protein-based COVID-19 vaccine NVX-CoV2373, the company shared new data this week on the vaccine’s efficacy against the South African B.1.351 variant.
Novavax published the latest results from a Phase IIb clinical trial conducted in South Africa evaluating the safety and efficacy of NVX-CoV2373, appearing in the NEJM’s May 6, 2021 issue. The results show that the COVID-19 vaccine candidate has an efficacy of 51 percent against the B.1.351 variant, which emerged out of South Africa and is currently the dominant variant in the country.
Earlier results from a more complete analysis of trial data shared in March confirmed a high level efficacy of 86.3 percent against the B.1.117 UK variant. These results came from data from Novavax’s Phase III UK trial where B.1.117 is the dominant strain. That analysis also showed that the Novavax COVID-19 vaccine was 96.4 percent effective against the original SARS-CoV-2 strain, 89.7 percent effective overall and 100 percent protective against severe disease, including all hospitalizations and deaths (across both the UK and South African trials).
In addition to efficacy data for B.1.351, the latest analysis also shows that prior infection with the original strain of SARS-CoV-2 does not protect against subsequent infection by the B.1.351 variant, as seen through 60 days of follow up. However, additional follow-up data obtained for the complete analysis of the South Africa trial shows there may be a modest protective effect of prior exposure with the original COVID-19 strain.
Despite the less then stellar efficacy posted against B.1.351 in the latest results for Novavax’s vaccine, “This data publication reinforces the encouraging safety profile and cross-protective effect across variants seen in studies of our vaccine to-date,” said Dr. Gregory M. Glenn, president of research and development at Novavax, in a news release. “It also demonstrates that ongoing evaluation of COVID-19 vaccine efficacy against SARS-CoV-2 variants is urgently needed to inform vaccine development and use.”
We should also bear in mind that we have possibly been spoiled by high COVID-19 vaccine efficacies, particularly given that the World Health Organization (WHO) and FDA had both set the bar at 50 percent effectiveness for any candidate COVID-19 vaccine to be eligible for authorization or approval.
The efficacy, safety and immunogenicity of the Novavax COVID-19 vaccine is being evaluated in a Phase IIb randomized, observer-blinded, placebo-controlled trial being conducted in South Africa among healthy adults, and in a small cohort of medically stable adults living with human immunodeficiency virus (HIV). An overall efficacy of 49 percent was confirmed in the latest, complete analysis, as it was the same as the initial analysis.
Among healthy adults without HIV, NVX-CoV2373 demonstrated 60 percent efficacy 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. In the complete analysis, the B.1.351 variant continued to be the dominant circulating strain. Importantly, all five cases of severe disease observed in the trial occurred in the placebo group.
NVX-CoV2373 is a protein-based vaccine candidate engineered from the genetic sequence of the first, “original” strain of SARS-CoV-2. It was made using Novavax’s recombinant nanoparticle technology to generate antigen derived from the coronavirus spike (S) protein and contains Novavax’s patented saponin-based Matrix-M as an adjuvant to enhance the immune response and stimulate high levels of neutralizing antibodies.
NVX-CoV2373 contains purified protein antigen and can neither replicate, nor can it cause COVID-19. In preclinical studies, NVX-CoV2373 induced antibodies that blocked the binding of the coronavirus spike protein to cellular receptors and provided protection from infection and disease. It was generally well-tolerated and elicited robust antibody response in Phase I/II clinical testing.
In addition to the UK and South African trials, NVX-CoV2373 is being evaluated in the US and Mexico in the PREVENT-19 trial, which commenced in December 2020. There is also a Phase I/II continuation trial being conducted in the US and Australia.