On May 21, 2021, Novavax announced participation in a mix-and-match (vaccine interchangeability) COVID-19 vaccine booster trial that led by the University Hospital Southampton NHS Foundation Trust and other UK National Institute for Health Research sites.

Novavax’ recombinant protein vaccine candidate, NVX-CoV2373, was one of seven COVID-19 vaccines studied to evaluate the potential for providing a booster dose from different manufacturers in people who have previously received two doses of an authorized vaccine.