Novavax has reported that an initial two-dose series of its Covid-19 vaccine, NVX-CoV2373, showed cross-reactive immune responses against Omicron and other variants of the SARS-CoV-2 virus.
These responses were observed to be amplified on administering a third dose of the vaccine at six months.
A protein-based vaccine developed from the genetic sequence of the first viral strain, NVX-CoV2373 also contains a saponin-based Matrix-M adjuvant.
Findings showed that anti-spike IgG and ACE2-inhibition titers following booster rose 9.3-fold and 19.9-fold (Omicron), respectively versus peak responses reported following a two-dose vaccine regimen.
Following two doses of the vaccine, wild-type neutralisation responses for prototype, Delta and Omicron variants were reported.
A substantial rise was noted on boosting with a third dose, with titers for Delta and Omicron in line with levels linked to protection seen in Phase III trials in the US, UK and Mexico.
Omicron wild-type neutralisation was observed to be <4-fold lower than prototype following two vaccine doses, indicating that a booster shot as well as a vaccine for Omicron variant could be useful.
Meanwhile, findings from Phase III PREVENT-19 trial in the US and Mexico showed substantial immune responses in adolescents after a two-dose vaccine regimen, including enhanced IgG and receptor inhibition titers against a wide range of variants, including Omicron.
Novavax Research and Development president Gregory Glenn said: “We are encouraged that boosted responses against all variants were comparable to those associated with high vaccine efficacy in our Phase III clinical trials, suggesting that NVX-CoV2373 can play an important role in the ongoing fight against new variants.”
“Novavax has cloned, expressed and characterised the Omicron spike protein vaccine and will soon enter the GMP-phase of production. We expect to begin clinical studies in the first quarter of 2022.”
Novavax administered the first booster doses of its vaccine in an extension of its Phase III PREVENT-19 trial.