A study in the United Kingdom into using different COVID-19 vaccines in two-dose inoculations is being expanded to include shots made by Moderna and Novavax, researchers say.
The trial, known as the Com-Cov study, was first launched in February to look at whether giving a first dose of one type of COVID-19 shot and a second dose of another, elicits an immune response that is as good as using two doses of the same vaccine.
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The idea, said Matthew Snape, the Oxford University professor leading the trial, “is to explore whether the multiple COVID-19 vaccines that are available can be used more flexibly”.
The UK and many other countries in Europe are currently using the Oxford-AstraZeneca and Pfizer-BioNTech COVID vaccines in nationwide immunisation campaigns against the coronavirus pandemic.
But reports of very rare blood clots have prompted some governments – including France and Germany – to say the Oxford-AstraZeneca shot should only be given to certain age groups, or that people who have had a first dose of AstraZeneca’s vaccine should switch to a different one for their second dose.
In a briefing about the expansion of the study to include Moderna’s and Novavax’s COVID-19 vaccines, Snape, an associate professor in paediatrics and vaccinology at Oxford, said it will seek to recruit adults aged over 50 who have received their first, or “prime”, vaccination in the past 8-12 weeks.
These volunteers, who will have received either the Oxford-AstraZeneca or Pfizer-BioNTech vaccine, will be randomly allocated to get either the same vaccine or the Moderna or Novavax vaccine for a second dose.
The six new arms of the trial will each involve 175 people, adding a further 1,050 recruits in total, Snape said.
“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,” Snape said.
“This would also create resilience within the system in the event of a shortfall in availability of any of the vaccines.”
Results from the original mixing trial, using Oxford-AstraZeneca and Pfizer-BioNTech shots only, are expected as early as April or May, while results of the second phase should come in July.