A phase 1/2 trial of a recombinant SARS-CoV-2 nanoparticle vaccine revealed that the adjuvanted vaccine elicited immune responses which exceeded levels from COVID-19 convalescent serum, according to results published in the New England Journal of Medicine.
The primary analysis included 131 healthy participants randomised to receive the trimeric full-length SARS-CoV-2 spike glycoprotein (NVX-CoV2373) vaccine in 5 μg and 25 μg doses with Matrix-M1 adjuvant, (n=83) without adjuvant (n=25), or with placebo (n=23), in two intramuscular injections, 21 days apart. The primary outcomes were reactogenicity and laboratory values (serum chemistry and haematology) to assess safety, and the IgG anti-spike protein response. Secondary outcomes included unsolicited adverse events, wild-type virus neutralisation, and T-cell responses.
According to the results, no serious adverse events were noted. Reactogenicity was absent or mild in the majority of participants (more common with adjuvant) and was of short duration. The addition of adjuvant resulted in enhanced immune responses, was antigen dose-sparing, and induced a T helper 1 (Th1) response. The two-dose 5-μg adjuvanted regimen induced immune responses that exceeded levels in COVID-19 convalescent serum.
These findings indicate that the adjuvanted vaccine NVX-CoV2373 is a promising candidate that warrants testing in efficacy studies, the authors say.