Matching Pfizer and Moderna, Novavax unveiled final results Thursday afternoon from its Covid-19 vaccine trials in the UK and South Africa, showing its candidate proved to be 96% effective against mild, moderate and severe Covid-19 cases in the UK.
And while the vaccine posted just 50% efficacy against the South African variant, across both trials the shot demonstrated complete protection against severe Covid-19, including all hospitalizations and deaths, Novavax said. But with only five severe cases occurring in the placebo arms of each trial, some physicians are questioning whether that’s enough data to actually show complete protection.
“The FDA has asked for at least five severe cases in the placebo group, so this is pretty minimum,” Walid Gellad, director of the University of Pittsburgh’s Center for Pharmaceutical Policy and Prescribing, told Endpoints News. “But here it’s five in each trial, so 10 total? If that’s the case, then that’s pretty convincing that it’s protective against severe disease, but I would want more certainty about that for each variant rather than in combination.”
The results for the Maryland-based company come as it readies the release of more data next month from a US and Mexico-based trial of 30,000 participants. The US government is hoping for positive results, after forging a $1.6 billion deal with Novavax in July to allow for the purchase of 100 million doses.
Overall for the UK trial, the company said there were 106 cases of Covid-19 among the more than 15,000 participants, with 10 cases in the vaccine group and 96 in the placebo group. For the variant circulating in the UK, the vaccine’s efficacy was 86.3%, Novavax said.
Also similar to the Pfizer, Moderna and Johnson & Johnson vaccines that offer some protection after the first shot, Novavax said that 14 days after its first dose, vaccine efficacy was 83.4% in the UK.
In South Africa, however, a complete analysis of the vaccine’s efficacy revealed 147 PCR-positive Covid-19 cases in the trial, including 51 in the vaccine group and 96 in the placebo group, which works out to an overall efficacy of 48.6% against predominantly variant strains (and 55.4% efficacy among HIV-negative participants). Fourteen days after the first dose, the company found about 43% efficacy in the South African trial. The company said that the vast majority of cases circulating during the efficacy analysis were due to the variant in South Africa.
“The vaccine results coming out now will give us a dose of reality, that maybe the older studies do not (because they dealt with original variants),” Gellad said. “We are in a race against time to vaccinate, and we have to continue to do everything we can to reduce transmission.”
In addition to the final results from the UK and South Africa, Novavax also noted some potentially promising information on how prior Covid-19 infections with the original strain might offer some later protective effects against the variant circulating in South Africa.
“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 said of the South African trial.
