Novavax Initiates COVID-19 Vaccine Clinical Trial Crossover

• Crossover allows participants to continue in trials and remain blinded
• Ensures that all trial participants receive active vaccine
• South Africa and UK crossover arms initiated; US/Mexico PREVENT-19 crossover planned

GAITHERSBURG, Md., April 5, 2021 /PRNewswire/ -- Novavax, Inc. (Nasdaq: NVAX), a biotechnology company developing next-generation vaccines for serious infectious diseases, today announced the initiation of crossover arms in two ongoing clinical trials of NVX-CoV2373, the company's COVID-19 vaccine candidate. Crossover ensures the administration of active vaccine to all participants in the trials and has begun for Novavax' Phase 2b trial in South Africa and its pivotal Phase 3 trial in the United Kingdom.

Under Novavax' updated clinical trial protocols[1], all participants in the UK and US Phase 3 trials will be offered the opportunity to receive an additional round of injections. Participants who elect to do so will receive an additional two-dose regimen of either vaccine (for those who originally received placebo) or placebo (for those who originally received vaccine). Participants in the South Africa Phase 2b trial will receive either active vaccine for those who initially received placebo, or a booster dose of active vaccine for those who initially received active vaccine. Participants across all three trials will remain blinded to their courses of treatment to preserve the ability to assess efficacy in each trial, and all will be followed for up to two years to monitor the safety and durability of protection the vaccine. In the trials taking place in South Africa and the United Kingdom, half of the participants initially received the active vaccine while two-thirds of participants in PREVENT-19, the trial being conducted in the US and Mexico, initially received active vaccine.

"The crossover arms ensure that all participants have access to an active vaccine candidate while allowing Novavax to continue to monitor the safety and efficacy of our vaccine over the long term," said Filip Dubovsky, M.D., Chief Medical Officer, Novavax. "We are grateful to the volunteers who stepped forward to take part in our clinical trials, without whom we would be unable to develop, study and ultimately deliver what we hope will be a significant tool in the fight against COVID-19."