A Phase III trial carried out in the UK showed that the Novavax vaccine was effective at preventing 89.3% of infections, even as half of the cases were of the new British variant. The South African variant, however, is proving a different problem.

The Novavax vaccine has been running trials in Britain, South Africa, the United States and Mexico. The trial in Britain, involving over 15,000 people, was found to be 89.3% effective at preventing COVID-19. Researchers calculated its efficacy against the new British variant at 86%, while its efficacy against the original COVID-19 strain was calculated to be 95.6%.

The data is based on 62 confirmed cases, of which 56 were in the placebo group, and just 6 in the group that received the vaccine. Out of these, just 1 case was severe, in the placebo group. The results are particularly encouraging as they also consider the new British variant, which is currently believed to be much more infectious than the original strain.

“We have the first trial — we are the first to conduct an efficacy trial — in the face of a changing virus,” Stanley Erck, the president and chief executive of Novavax, told NYT, adding that he was expecting lower efficacy against the variants, and that these positive results are a “bit of a surprise.”

However, while the Novavax vaccine does seem to work excellently against the British variant, the same thing can’t be said about the South African strain. The South African trial was relatively small (just 4,400 volunteers) and it was not meant to deliver a precise estimate of vaccine efficacy. Even so, the results are clearly concerning, as the efficacy rate was under 50%. “You’re going to have to make new vaccines” for this strain, Mr. Erck said. The trial was also not robust enough to reliably demonstrate whether the vaccine can protect against the most severe of cases, another measure of how well a vaccine works.

Novavax is already working on a modified vaccine version for the existing variants, but this shows the need to vaccinate as many people as quickly as possible, before new (potentially even more dangerous) variants emerge. But even so, a 50% efficacy is (while far from perfect) still way better than zero.

“This is the first COVID-19 vaccine for which we now have objective evidence that it protects against the variant dominating in South Africa,” says Professor Shabir Maddi, Executive Director of the Vaccines and Infectious Diseases Analytics Research Unit (VIDA) at Wits, and principal investigator in the Novavax COVID-19 vaccine trial in South Africa. “I am encouraged to see that Novavax plans to immediately begin clinical development on a vaccine specifically targeted to the variant, which together with the current vaccine is likely to form the cornerstone of the fight against COVID-19.”

The other Phase III trials from Novavax are expected to release results very soon, while results new trials carried on the other strains are expected in the second quarter of 2021. The company expressed confidence in its ability to scale production and adapt to new variants.

“A primary benefit of our adjuvanted platform is that it uses a very small amount of antigen, enabling the rapid creation and large-scale production of combination vaccine candidates that could potentially address multiple circulating strains of COVID-19,” said Gregory M. Glenn, M.D., President of Research and Development, Novavax. “Combined with the safety profile that has been observed in our studies to-date with our COVID-19 vaccine, as well as prior studies in influenza, we are optimistic about our ability to rapidly adapt to evolving conditions.”

Novavax, a company few had heard of before the pandemic, has been one of the leaders in the vaccine race since the start, but its large-scale trials lagged a bit, making it deliver results after the likes of Pfizer and Moderna. However, unlike both these two (which use mRNA technology) and the AstraZeneca vaccine (which is adenovirus-based), the Novavax vaccine is protein-based. The two-jab Novavax vaccine teaches the immune systems to make antibodies to the spike protein while only exposing the body to the protein itself — not the actual virus — so there is no risk of infection.

Despite positive results, however, it’s not yet clear when the vaccine would be approved for emergency use. The US FDA isn’t willing to review an emergency use authorization without domestic results, and so far, the company has randomized 16,000 North American patients (out of a goal of 30,000 patients).