A major UK study examining whether Covid vaccines can be safely mixed with different types of jabs for the first and second doses is to be expanded.
Researchers running the Com-Cov study, launched in February to investigate alternating doses of the Oxford/AstraZeneca and Pfizer vaccines for the first and second doses, will now include a shot of Moderna or Novavax.
The study is examining whether mixing vaccines might give broader, longer-lasting immunity against the virus and new variants of it, and offer more flexibility in the administration of vaccines.
Led by the University of Oxford, the study will seek to recruit adults aged over 50 who have received their first vaccination in the past eight to 12 weeks.
Matthew Snape, associate professor in paediatrics and vaccinology at the University of Oxford, who is chief investigator on the trial, 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.
“This would also create resilience within the system in the event of a shortfall in the availability of any of the vaccines in use.”
The volunteers, who will have received either the Oxford/AstraZeneca, or Pfizer/BioNTech vaccine, will be randomly allocated to receive either the same vaccine for their second dose or a dose of the jabs produced by Moderna or Novavax.
The Moderna jab has started being rolled out across the UK, and the Novavax jab manufactured by GlaxoSmithKline (GSK) is under review by the Medicines and Healthcare products Regulatory Agency (MHRA).
The six new arms of the trial will each recruit 175 candidates, adding 1,050 recruits to the programme. The researchers will study any adverse reactions and the immune system responses to these new combinations of vaccines.
If the study shows promising results, the MHRA and Joint Committee on Vaccination and Immunisation (JCVI) would formally assess the safety and efficacy of any new vaccination regimen before it is rolled out to patients.
Prof Snape said he hoped the results of the second part of the study would be available in June or July, with the first part expected to report results next month.
He told a press briefing: “What I’m hoping is that we won’t rule out any combinations. That’s how we need to look at it – are there any combinations we shouldn’t be giving because they don’t generate a good immune response, and I’m hoping that won’t be the case.
“And that will give us lots of flexibility, not just in the UK, not just in Europe where we’re looking about restricting uses of some vaccines for some age groups, but across the world, where we have, perhaps, a little bit more intermittent supply of vaccines, not as reliable.”
ProfJeremy Brown, a member of the JCVI, said people will eventually “have to” mix Covid-19 jabs.
He told BBC Radio 4’s Today programme: “It’s practically going to have to be that way because, once you’ve completed a course of, say, the Moderna or Pfizer or the AstraZeneca with two doses, in the future it’s going to be quite difficult to guarantee you get the same type of vaccine again.”