The booster is indicated for use after a minimum of six months following a vaccine regimen with an authorised or approved Covid-19 shot.
NVX-CoV2373 can be given to people for whom an mRNA bivalent Covid-19 booster vaccine, authorised by the FDA, is either not clinically appropriate or accessible.
The regulatory agency based its decision on findings from the Phase III Prevent-19 clinical trial, as well as from the COV-BOOST trial, sponsored by the UK.
In the Phase III trial, the vaccine booster was given to healthy adult subjects nearly eight or 11 months following the primary regimen.
According to the findings, antibody levels following a booster shot rose substantially compared with pre-boost levels, growing above levels associated with protection in the Phase III studies.
Additionally, a 34 to 27-fold rise in neutralising antibodies was seen versus pre-boost levels on administering booster at eight or 11 months.
NVX-CoV2373 elevated antibody titers when administered as a third shot after a preliminary regimen with an authorised Covid-19 vaccine in the COV-BOOST trial.
Novavax president and CEO Stanley Erck said: “The US now has access to the Novavax Covid-19 vaccine, adjuvanted, the first protein-based option, as a booster.
“According to CDC data, almost 50% of adults who received their primary series have yet to receive their first booster dose.
“Offering another vaccine choice may help increase Covid-19 booster vaccination rates for these adults.”
In July this year, the company received FDA EUA for the NVX-CoV2373 vaccine for use as a two-dose primary regimen in adults.