Washington — U.S. biotech firm Novavax said Thursday its two-shot COVID-19 vaccine showed an overallin a major Phase 3 clinical trial in Britain and remained highly effective against a variant first identified there. But the positive news was offset somewhat by other results that showed it offered less protection against a highly transmissible variant of the first identified in South Africa.
Like the U.K. strain, the variant first found in South Africa is now spreading rapidly around the world, and the first cases have been confirmed in the U.S. There have been concerns in recent weeks that the vaccines developed around the world could be less effective against the South Africa variant in particular, and while the Novavax trial results appear to confirm some level of resistance, both the company and an outside health expert were optimistic about the level of protection provided against both new strains.
"NVX-CoV2373 has the potential to play an important role in solving this global public health crisis," said the company's president and CEO Stanley Erck, using Novavax's name for the vaccine. "We look forward to continuing to work with our partners, collaborators, investigators and regulators around the world to make the vaccine available as quickly as possible."
British Prime Minister Boris Johnson tweeted that the results were "good news," adding that U.K. drug regulators would now assess the vaccine for potential approval.
The vaccine was one of six candidates backed by a U.S. government project formerly known as Operation Warp Speed, which provided the Maryland-based company $1.75 billion. It's also being tested in a trial in the U.S. and Mexico, which has recruited about 16,000 of 30,000 participants thus far.
Unlike the Pfizer, Moderna and AstraZeneca vaccines, which deliver the genetic instructions that make human cells create a key protein of the virus, the Novavax shot injects the proteins directly into the body to evoke an immune response.
"Pretty good" vs. South Africa strain
The British trial involved 15,000 people aged 18 to 84, including 27% who were over the age of 65. The first interim analysis was based on 62 cases of confirmed COVID-19 among participants, of which 56 cases were observed in the placebo group versus six cases among people who received the vaccine.
The company's preliminary analysis indicated the variant first identified in the U.K., called B.1.1.7, was detected in more than 50% of the confirmed cases. Novavax said the results showed their vaccine was 95.6% effective against the original COVID-19 strain, and 85.6% against the U.K. variant.
But the level of protection was lower in a smaller, mid-stage trial conducted in South Africa. That study enrolled just over 4,400 patients from September to mid-January, during which time the B.1.351 variant, which contains critical mutations along the virus' spike protein, was spreading rapidly through the country.
Overall efficacy was 49.4% in this trial, but that figure rose to 60% among the 94% of trial participants who were HIV-negative.
Worryingly, Novavax said about a third of participants in the South Africa trial had been previously infected with the original form of the virus, while the subsequent infections during the study were largely from the variant.
The results come just days after South African researchers told CBS News that the new strain in the country appearedin blood samples from people who were infected by the original strain of the virus, first detected in Wuhan, China late in 2019. That research left the scientists concerned that previous infection could provide little immunity to the new South Africa variant, and possible impact the efficacy of the vaccines.
Amesh Adalja, a doctor and senior scholar at the Johns Hopkins Center for Health Security, told AFP, however, that it was important to keep the decreased efficacy in perspective, and the vaccine was still a success.
"Sixty percent against the variant is still pretty good," he said. "Clearly, the Novavax vaccine prevented severe disease, which is really in the end what matters the most."
Professor Shabir Madhi, who's running the South African trials, said Thursday evening that the Novavax results were something "he did not dream of" when he saw how poorly the natural immunity from the first wave of COVID infections, with the original strain, fared against the variant in South Africa.
Novavax CEO Erck called the preliminary efficacy results from the South Africa trial, "above people's expectations."
The studies in Britain and South Africa were the first to assess a COVID-19 vaccine's performance against both the U.K. and South Africa variants in real world trials.
Moderna has previously said that itsagainst both of the new, highly infectious variants, but the study it cited was based on lab research, not real world testing against human infection.
Pfizer has alsothat suggest its vaccine will prove effective against the U.K. variant, but it has not yet revealed any data for testing against the strain prevalent in South Africa.