UK trial evaluating ‘mix and match’ COVID-19 vaccine regimens expanded

A UK trial evaluating the safety of mixing different COVID-19 vaccines is set to be expanded to include Moderna and Novavax’s respective jabs.

The Com-Cov study, announced earlier this year, is the first trial in the world to evaluate the effects of using different COVID-19 vaccines for the first and second dose within a two-dose vaccination regimen.

It is designed to monitor the impact of the different dosing regimens on immune responses. It is being run by the National Immunisation Schedule Evaluation Consortium (NISEC) across eight National Institute for Health Research (NIHR) supported sites.

Researchers will gather immunological evidence on different intervals between the first and second dose for a mixed-vaccine regimen against control groups when the same vaccine is used for both doses.

According to the BBC, over 800 people are already enrolled in the study and have received two doses of either the Pfizer vaccine, AstraZeneca vaccine or a mix of the two.

Initial finds from the trial are expected to be published in the summer, with the study set to run for 13 months in total.

"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,” Matthew Snape, chief investigator of the trial, told the BBC.

"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,” he added.