Early studies of a vaccine containing 5 micrograms (ug) of a recombinant nanoparticle SARS-CoV-2 spike protein plus 50 ug of Matrix-M (a saponin-based adjuvant containing cholesterol and phospholipid) showed that a two-dose regimen administered 21 days apart caused a robust immune response in healthy adults. Recently, investigators reported the results of a large efficacy trial of the vaccine (NVX-CoV2373, Novavax) (Heath PT, Galiza EP, Baxterm DN, et al. Safety and efficacy of NVX-CoV2373 Covid-19 vaccine. N Engl J Med. 2021 Sep 23;385:(13):1172-1183).

A phase 3, randomized, controlled clinical trial was conducted at 33 sites in the United Kingdom during which time the alpha variant of SARS-CoV-2 was the prevalent, circulating strain. About 14,000 participants were divided in half and given either the two-dose vaccine 21 days apart or placebo. Among participants, 28% were 65 years of age or older and 45% had co-existing illnesses. COVID-19 infections (either mild, moderate, or severe) were reported in 10 participants in the vaccine group and 96 in the placebo group for a vaccine efficacy of 89.7%. Five cases of severe disease were reported; all were in the placebo group. Reactogenicity was generally mild and transient. Among participants who were 65 years of age or older, vaccine efficacy was 88.9%.

Investigators concluded, “A two-dose regimen of the NVX-CoV2373 vaccine administered to adult participants conferred 89.7% protection against SARS-CoV-2 infection and high efficacy against the B.1.1.7 [alpha] variant.”

Pending review by the FDA and CDC, the Novavax vaccine adds another potential weapon in the fight against this pandemic.

Materials in this section are updated as new information and vaccines become available. The Vaccine Education Center staff regularly reviews materials for accuracy.

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