Novavax’s COVID-19 vaccine is effective against emerging SARS-CoV-2 variants

Novavax Inc. has revealed that in a Phase III trial its NVX–CoV2373 vaccine candidate was 96.4 percent effective against mild, moderate and severe disease caused by the original COVID-19 strain in the UK and 86.3 percent effective against the B.1.1.7 SARS-CoV-2 variant. SARS-CoV-2 is the virus that causes COVID-19.

Additionally, the company reported that the final efficacy in its Phase IIb trial taking place in South Africa was 55.4 percent among the HIV-negative trial participants. The majority of infections in this region are B1.351 escape variants. Across both trials, NVX-CoV2373 demonstrated 100 percent protection against severe disease, including all hospitalisation and death.

“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,” commented Stanley Erck, President and Chief Executive Officer of Novavax. “Today marks one year since the WHO officially declared the COVID-19 pandemic, and with this data in hand, we are even more motivated to advance our vaccine as a potential weapon in the fight to end the suffering caused by COVID-19.”

About the UK trial

The Phase III trial enrolled >15,000 participants aged 18 to 84 years of age. The primary endpoint of the study is based on the first occurrence of PCR-confirmed symptomatic COVID-19 with onset at least seven days after the second study vaccination in serologically negative (to SARS-CoV-2) adult participants at baseline.

The vaccine’s efficacy was 96.4 percent against the original strain and dropped to 86.3 percent against the B.1.1.7/501Y.V1 variant circulating in the UK. The overall efficacy is 89.7 percent, with 106 COVID-19 cases observed in the trial, 10 in the vaccine group and 96 in the placebo group. NVX-CoV2373 was effective against severe disease: five severe cases were observed in the study, all occurred in the placebo group. Four of the five severe cases were attributed to the B.1.1.7/501Y.V1 variant.

Additionally, the investigators reported that 14 days after the first dose, the vaccine efficacy was 83.4 percent.

About the South Africa Phase IIb study

The South Africa trial was a randomised, observer-blinded, placebo-controlled Phase IIb  trial of NVX-CoV2373. One cohort evaluated efficacy, safety and immunogenicity in approximately 2,665 healthy adults, the other evaluated the same in approximately 240 medically stable, HIV-positive adults.

A complete analysis of vaccine efficacy among 147 PCR-positive cases (51 cases in the vaccine group and 96 in the placebo group) demonstrated an overall efficacy of 48.6 percent against predominantly variant strains. The vast majority of cases circulating during the efficacy analysis were due to the B.1.351/501Y.V2 variant circulating in South Africa. All five cases of severe disease observed in the trial occurred in the placebo group.

Among HIV-negative participants, the vaccine was 55.4 percent effective. The complete analysis shows that vaccine-induced protection began 14 days after the first dose, but increased efficacy was observed seven days after the second injection.

In both the UK and South African trials the vaccine is well-tolerated, with low levels of severe, serious (SAEs) and medically attended adverse events at day 35.