- The Novavax coronavirus vaccine is nearly 90 percent effective at preventing COVID-19.
- It was less effective at preventing infections caused by the B.1.351 variant dominating in South Africa.
- The vaccine, which produces a robust immune response, was effective at preventing severe cases of COVID-19.
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Results from two clinical trials evaluating Novavax’s coronavirus vaccine show the shot is nearly 90 percent effective at preventing COVID-19.
The vaccine worked well against all variants but was less effective at preventing infections caused by the B.1.351 variant dominating South Africa.
One of the trials, conducted in the United Kingdom, found the vaccine to be effective against the highly transmissible variant B.1.1.7, which was detected in the country in late December.
The other clinical trial took place in South Africa, where cases are largely linked back to the B.1.351 variant.
According to a press release published Thursday by Novavax, the vaccine did confer protection against the South African variant. Still, it was less powerful at preventing infections caused by B.1.351 than the original variants.
Efficacy dropped to 60 percent when tested primarily against the B.1.351 variant in South Africa.
Still, the findings are promising and show the vaccine produces a robust immune response capable of identifying and targeting new variants.
“This is the first COVID-19 vaccine for which we now have objective evidence that it protects against the variant dominating in South Africa,” Professor Shabir Maddi, the principal investigator in the Novavax COVID-19 vaccine trial in South Africa, stated in the press release.
The full analysis of the vaccine’s safety and efficacy has not yet been published.
More than 15,000 volunteers were recruited for the Novavax trial in the United Kingdom. The vaccine prevented 9 out of 10 infections, which included the original coronavirus variants and the B.1.1.7 variant detected in the United Kingdom in December.
The vaccine was 95.6 percent effective against the original variant and 85.6 percent effective against the B.1.1.7 variant, bringing the overall efficacy in the U.K. trial to 89.3 percent.
The trial in South Africa included 4,400 volunteers and was 60 percent effective at preventing COVID-19.
Twenty-nine people in the placebo group and 15 people in the vaccinated group developed COVID-19.
All of the cases were mild or moderate, with the exception of one severe case that occurred in someone in the placebo group.
Scientists suspect the multiple mutations on the B.1.351 variant contributed to the reduction in vaccine efficacy.
“The efficacy likely dropped because the vaccine isn’t completely matched to the strain. However, it’s critical to realize that the vaccine still prevented severe disease, which is the whole point of vaccination,” said Dr. Amesh Adalja, a senior scholar at the Johns Hopkins University Center for Health Security and an infectious disease expert.
This is true for the new variant detected in the United Kingdom and the one discovered in South Africa, Adalja added.
Novavax is already tweaking its vaccine to target the variant better and plans to test it during the second quarter of 2021.
“Novavax uses a recombinant technology platform so, if needed, it could be easily adjusted,” Adalja said.
A third clinical trial that will test the vaccine in 30,000 people is being conducted in the United States and Mexico. Those results won’t be released for several months.
The Novavax vaccine is a protein subunit vaccine. It uses a synthetic coronavirus spike protein to teach the immune system to produce antibodies that can deactivate the coronavirus if a person were to be exposed.
The B.1.351 variant contains multiple mutations within the spike protein, the part of the virus that latches onto human cells, which could make it trickier for the vaccine to do its job.
Dr. Benjamin Neuman, a professor of biology and Global Health Research Complex chief virologist at Texas A&M University, said the SARS-CoV-2 spike protein and the receptor it binds to, ACE2, fit together like spoons.
The B.1.351 variant has mutations at both ends of that groove that allow it to secure a tighter fit onto the ACE2 receptor.
These changes to the structure of the spike protein make it more difficult for the antibodies produced by the vaccine to bind to the groove, which is necessary to prevent infection.
“A well-trained immune response will make some antibodies that can stick to the groove in the top of the spike in a way that stops ACE2 from being able to bind, but to do that, the antibodies need to be able to exactly match the shape of small patches on the groove, which can change as the virus mutates,” Neuman explained.
Neuman said this is why “some people with immunity to an older strain of the virus or one of the vaccines, which all use the oldest available strain of the virus, may not have as much protection against B.1.351.”
Fortunately, these changes to the spike protein impact only a small population of the protective antibodies produced in response to the vaccine.
The vaccine teaches other parts of our immune system to protect us against the novel coronavirus, Neuman said, so while the vaccine may offer a little less protection against B.1.351, “people should still be protected for the most part.”
All things considered, 60 percent efficacy is pretty good.
The vaccine will help prevent many infections, and most importantly, cases with severe disease.
If the B.1.351 variant becomes the dominant variant, the lower efficacy means it will take more vaccinations to achieve herd immunity.
Originally, scientists would have been pleased to see a COVID-19 vaccine with 60 percent efficacy and were pleasantly surprised when the messenger RNA (mRNA) vaccines appeared to be over 90 percent effective.
“Early on, we would have accepted 50% efficacy at preventing symptomatic disease. We’ve been spoiled by Moderna and Pfizer’s success,” Adalja said.
The Novavax vaccine will be an important addition in our fight against COVID-19, said Adalja.
One major benefit is that it can be stored in cool refrigerated temperatures rather than the freezers needed to store the Moderna and Pfizer vaccines. The Novavax vaccine also arrives ready to use in liquid form, which will be helpful in expanding access to the vaccines.
Neuman said having several available vaccine options will strengthen our overall vaccination efforts.
“The mRNA vaccines would be the most delicate, but may provide the strongest immunity, while the adenovirus and protein vaccines like Novavax look like a good compromise in terms of being able to get good protection to out-of-the-way places,” Neuman said.
The Novavax coronavirus vaccine is nearly 90 percent effective at preventing COVID-19. Though the vaccine worked against all variants, it was less effective at preventing infections caused by the B.1.351 variant dominating in South Africa. Still, the vaccine, which produces a robust immune response, was effective at preventing severe cases of COVID-19. Novavax is already working on a new vaccine that will target the new variant and expects to start testing it in a few months.