A trial exploring the possibility of mixing different Covid vaccines across first and second doses is being expanded. This major trial was initially launched to explore the potential benefits of mixing vaccines rather than using the same one for both the first and second vaccination.
Those running the trial are inviting over 50s who have already received a first dose of the Pfizer or AstraZeneca jab to apply if they wish to take part. Those who participate in the trial will either receive a second dose of the same vaccine or might receive the Novavax or Moderna vaccine. The study’s leaders are looking to recruit over 1,000 people who have had their first vaccine dose in the last 8-12 weeks.
Potential benefits of mixing vaccines
According to experts, several benefits may come from combining vaccines rather than using the same one for both doses. Potential benefits include broader immunity, longer-lasting effects, more protection against new variants, and more flexibility around the vaccine rollout.
Around 800 people have already signed up for the study; some have received two doses of one vaccine, with others receiving a combination of two different vaccines. Experts hope the results of the first part of the study will be available in May, with results from the expanded trial being available in June or July.
Those involved with the study have said that they are confident that mixing the vaccines is safe. However, the studies are designed to determine how effective doing so can be. Any reactions and side-effects will be monitored, and everyone taking part will have a blood sample tested to check for immune responses triggered by the vaccines.
Completing the rollout with greater speed
Another potential benefit of combining vaccines is that the rollout could be completed with greater speed and efficiency.
Professor Matthew Snape, the lead investigator in the trial, 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. What I'm hoping is that we won't rule out any combinations."
He added that being able to combine vaccinations would provide more flexibility within the UK and across Europe. According to the professor, it could mean getting all adults fully vaccinated far quicker.