Novavax shares in the red after vaccine sees 51% efficacy against South African COVID variant

While the world (and the biotech’s investors) wait for full data and possible filing for emergency use of Novavax’s NVX-CoV2373, it has dropped more data on how its shot works against a particular variant.

This was against the so-called South African variant, better known as B.1.351, which saw vaccine efficacy hit 51% in HIV-negative subjects of a midstage trial.

This efficacy dropped slightly in HIV-positive patients, to 43%, though given the nature of the disease and its impact on the immune system, this was not unexpected.

That headline 51% was enough to drive Novavax’s shares down more than 2% in after-hours trading Wednesday night and opened down 9% today, coming also on the news that the Biden administration is seeking to wave COVID vaccines patents in the hope it may speed up global access to the shots. Though we know B.1.351 has mutated in such a way that it can reduce the efficacy of vaccines, with numbers from mRNA vaccines hitting 90%-plus (though not against all variants), anything lower is seen as a poor read-through.

These latest results, published in the NEJM, were formed from a post hoc analysis with full data from the company's trial in South Africa, which included nearly 2,700 volunteers.

The average age, just 32, showed the trial was set for younger adults, who typically have a better time dealing with the virus, with the cases predominately mild to moderate.

These data also suggested prior infection with the original COVID-19 strain “did not protect against subsequent infection by the variant predominantly circulating in South Africa,” the biotech said.

RELATED: Novavax COVID-19 vaccine 90% efficacious in phase 3, but protection plummets against one variant

This was through 60 days of follow-up. However, with additional follow-up, “the complete analysis of the South Africa trial indicates that there may be a modest protective effect of prior exposure with the original COVID-19 strain,” it added.

This effectiveness is however lower than the data at the start of the year, which showed efficacy of just over 60% against symptomatic COVID in the South African trial. Though this was more mixed, with some having an early form of the virus as well as having the South African variant among those who were HIV-negative.

Back in January, Novavax’s vaccine achieved 89.3% efficacy in a phase 3 clinical trial that enrolled subjects exposed to the B.1.1.7 variant found in the U.K., a variant that has higher transmissibility but is not seen as being able to evade vaccines nor more lethal.

What still needs to be shown, and was not here, is how good NVX-CoV2373 is at preventing severe disease or hospitalization. The trial was, however, specifically set up to see how the vaccine performed in people who were HIV-negative and -positive.