Novavax has reported that data from a pivotal Phase III trial of its vaccine candidate, NVX–CoV2373, in the UK showed an efficacy of 96.4% against mild, moderate and severe disease caused by the original Covid-19 strain.

A protein-based vaccine candidate, NVX-CoV2373 is engineered from the genetic sequence of SARS-CoV-2.

The Phase III trial enrolled over 15,000 subjects aged between 18 and 84 years.

Data showed that the vaccine’s efficacy was 96.4% against the original virus strain and 86.3% against the B.1.1.7/501Y.V1 variant circulating in the UK.

The primary efficacy endpoint showed an overall vaccine efficacy of 89.7%. Of 106 cases detected, ten were in the vaccine arm while 96 in the placebo arm.

The randomised, observer-blinded, placebo-controlled South Africa Phase IIb clinical trial of NVX-CoV2373 had two cohorts. One cohort analysed efficacy, safety and immunogenicity in 2,665 healthy adult subjects while the second cohort analysed safety and immunogenicity in 240 medically stable, HIV-positive adults.

Data showed that the efficacy of 55.4% was observed among the HIV-negative trial participants in a region where the vast majority of strains are B1.351 escape variants.

In both trials, the vaccine showed 100% protection against severe disease, including hospitalisation and death and also achieved statistical success criteria.

The vaccine was well-tolerated with reduced levels of severe, serious (SAEs) and medically attended adverse events at day 35 balanced between the vaccine and placebo arms in the UK and South African trials.

Novavax president and CEO Stanley Erck said: “We are very encouraged by the data showing that NVX-CoV2373 not only provided complete protection against the most severe forms of disease, but also dramatically reduced mild and moderate disease across both trials.

“Importantly, both studies confirmed efficacy against the variant strains.”

In a separate development, ImmunityBio has announced the development of a novel hAd5 ACE2 Decoy therapeutic vaccine for neutralising the SARS-CoV-2 virus, including the E484K and N501Y mutations.

The hAd5 ACE2 Decoy candidate is based on modified ACE2 receptors that would compete with ACE2 on respiratory tract cells for binding of the virus.