Novavax has reported positive Phase I results from the Phase I/II clinical trial of its Covid-19 vaccine candidate performed in healthy participants aged 18-59 years.

The randomised, observer-blinded, placebo-controlled study assessed the vaccine candidate, named NVX‑CoV2373, with and without Matrix‑M adjuvant.

Data showed that the adjuvanted vaccine was generally well-tolerated and was able to trigger antibody responses numerically superior to that found in human convalescent sera.

Reactogenicity events with the product were generally mild. Tenderness and pain were the most frequent local symptoms after dose 1, with systemic events such as headache and fatigue being individually less frequent.

Meanwhile, greater reactogenicity was observed following dose 2 and majority of symptoms were ≤ Grade 1. Novavax said that the average duration of events was less than two days.

The investigators also tracked unsolicited adverse events through 28 days following dose 2. No severe (Grade 3) unsolicited adverse events were reported and majority of adverse events were mild with no link to vaccination.

Data did not reveal any serious adverse events (SAEs) and safety follow-up is ongoing.

A single dose of vaccine was able to generate anti-spike IgG antibodies in all participants and many subjects also developed wild-type virus neutralising antibody responses.

Following dose 2, all participants developed wild-type virus neutralising antibody responses, added the company.

The anti-spike IgG and viral neutralisation responses were favourably comparable to responses from patients with clinically significant Covid‑19.

Furthermore, the adjuvant was found to be dose-sparing, where the 5µg dose of NVX‑CoV2373 performed comparably with the 25µg dose.

Novavax Research and Development president Gregory Glenn said: “The Phase I data demonstrate that NVX-CoV2373 with our Matrix-M adjuvant is a well‑tolerated Covid-19 vaccine with a robust immunogenicity profile.

“Using a stringent wild-type virus assay performed by investigators at the University of Maryland School of Medicine, NVX‑CoV2373 elicited neutralising antibody titers greater than those observed in a pool of Covid‑19 patients with clinically significant disease.”

Funded by the Coalition for Epidemic Preparedness Innovations (CEPI), the trial was performed at two sites in Australia.