Earlier, the researchers had selected the Oxford-AstraZeneca vaccine and the Pfizer vaccine to investigate their alternating doses.
Supported by the UK Vaccines Taskforce, the investigator-initiated phase II clinical trial will analyse Novavax’s recombinant protein vaccine candidate NVX-CoV2373 as one of four Covid-19 vaccines.
It will assess the potential for combined regimens that mix vaccines produced by various companies to achieve immune protection against Covid-19.
A protein-based vaccine candidate, NVX-CoV2373 is engineered from the genetic sequence of SARS-CoV-2 and has Matrix-M adjuvant.
Novavax executive vice-president, chief medical officer Filip Dubovsky said: “Novavax’s addition to this important study reflects the urgency of finding innovative ways to protect as many people as possible in a dynamic pandemic landscape.”
The trial will enrol 1,050 adult subjects aged 50 years or above who received their first dose of a Covid-19 vaccine in the past eight to 12 weeks.
They will have received either the Oxford-AstraZeneca or Pfizer vaccine and will be randomly allocated to receive either the same vaccine for their second dose or a dose of the Covid-19 vaccines of Novavax or Moderna.
Novavax noted that 350 of the subjects will receive NVX-CoV2373.
The immune system responses from people receiving a heterologous regimen compared with those receiving a homologous regimen will be evaluated in the study.
University of Oxford Paediatrics and Vaccinology associate professor Matthew Snape said: “The focus of both this and the original COM-COV study is to explore whether the multiple Covid-19 vaccines that are available can be used more flexibly, with different vaccines being used for the first and second dose.
“If we can show that these mixed schedules generate an immune response that is as good as the standard schedules, and without a significant increase in the vaccine reactions, this will potentially allow more people to complete their Covid-19 immunisation course more rapidly.”