By Molly Walker, Deputy Managing Editor, MedPage Today
Novavax's two-dose COVID-19 vaccine had an overall efficacy of 90%, with 100% efficacy against moderate and severe disease, the manufacturer announced on Monday.
Data from a phase III trial in the US and Mexico found an overall efficacy of 90.4% against COVID-19, with 77 laboratory-confirmed cases of SARS-CoV-2 occurring at least 7 days after the second dose in serologically negative adults. Sixty-three of these cases were in the placebo group and 14 in the vaccine group, and the manufacturer stated that all cases in the vaccine group were defined as "mild" according to the trial protocol.
The placebo group had 10 moderate cases of COVID-19 and four severe cases, versus none in the vaccine group, for a vaccine efficacy of 100% against moderate to severe disease.
PREVENT-19 (Pre-Fusion Protein Subunit Vaccine Efficacy Novavax Trial / COVID-19) was a phase III study that enrolled 29,960 adults at 119 sites in the US and Mexico from January 25 to April 30, 2021. Participants were randomized 2:1 to receive two doses of Novavax's recombinant nanoparticle protein-based COVID-19 vaccine or a placebo.
The manufacturer stated that sequence data was available for 54 of 77 cases and that the vaccine met its secondary endpoint of 100% (95% CI 80.8-100) efficacy against virus strains not classified as variants of interest or concern. However, only 10 sequenced cases were not variants of interest or concern. Although the statement noted that the Alpha variant, B.1.1.7, was the “predominant” strain in the U.S., the manufacturer did not provide further details about the sequenced variants in its trial beyond the “variants of concern or interest.”
An exploratory analysis involving sequenced cases of variants of interest or concern, 38 in the placebo group and six in the vaccine group, demonstrated a vaccine efficacy of 93.2%.
The vaccine was also effective among "high-risk" groups, defined as adults over 65 with "certain comorbidities" or "life circumstances involving frequent exposure to COVID-19," the manufacturer said. There were 62 cases in the placebo group and 13 in the vaccine group, making the vaccine's efficacy in this population 91.0%.
Regarding safety, the vaccine was well tolerated, with comparable rates of serious and severe adverse events between groups, and no single adverse event reported by more than 1% of participants. The most common systemic side effects were fatigue, headache, and muscle pain, which did not last longer than two days.
Novavax said it plans to submit these results to a peer-reviewed publication and has already applied for emergency use authorization from the FDA.
A trial is being conducted among adolescents aged 12 to 17, and 2,248 participants recently enrolled, the company noted.