Novavax phase 3 vaccine study launched in the UK, South Africa, US, Mexico and Puerto Rico
On 28 December, a press statement from Novavax publicised the launch of a new phase 3 study being run by Novavax in the US, Mexico and Puerto Rico. This randomised controlled study will enrol approximately 30,000 participants. [1, 2]
It also reported a similar phase 3 study enrolling 15,000 participants at 33 sites in the UK. 
An earlier phase 2 study with 4,400 participants is ongoing in South Africa. 
The vaccine candidate – NVX-CoV2373 – contains a full-length S spike protein (produced in insect cells) with a saponin-based adjuvant to enhance the immune response and to boost antibodies. It is stable at 2°C to 8°C and can be distributed with regular refrigeration.
As with other approved vaccines, it does not include an active virus and cannot cause COVID-19.
Although many serious preexisting conditions including immunosuppression are exclusion criteria, it is important that HIV is not specifically listed.
However, these placebo controlled studies are taking place during the roll-out of the UK national vaccination programme.
This means that study participants who are offered an NHS vaccine should have the option to be unblinded to the study arm as part of their decision to take up this offer.
A similar arrangement has been agreed in the US for participants in the phase 3 Pfizer and Moderna studies. The Vaccine Transition Option allows for participants to become unblinded to whether they were in the placebo arm, and to be given the active vaccine. 
- Novavax announces initiation of PREVENT-19 pivotal phase 3 efficacy trial of COVID-19 vaccine in the United States and Mexico. (28 December 2020).
- ClinicalTrials.gov. A study looking at the efficacy, immune response, and safety of a COVID-19 vaccine in adults at risk for SARS-CoV-2.
- ClinicalTrials.gov. A study looking at the effectiveness, immune response, and safety of a COVID-19 vaccine in adults in the United Kingdom.
- ClinicalTrials.gov. A study looking at the effectiveness and safety of a COVID-19 vaccine in South African adults.
- Vaccine Transition Option.