UK expands Covid-19 mix and match vaccine trial

London: A study assessing the benefits of mixing and matching coronavirus vaccines has been extended to include the Moderna and Novavax jabs.

The Com-Cov study, led by the University of Oxford, has been investigating the immune responses of volunteers given a dose of the Oxford/AstraZeneca vaccine followed by the Pfizer jab, and vice versa, since February.

Now, an expanded study will seek to recruit adults aged over 50 who have received their first dose in the past eight to 12 weeks to test out the immune response when combined with one of the other vaccines as a second dose.

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, said Matthew Snape, associate professor in paediatrics and vaccinology at the University of Oxford and chief investigator on the trial.

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 availability of any of the vaccines in use,’ he said.

Six new arms of the trial will each recruit 175 candidates, adding a further 1,050 volunteers into the programme and the research will take place across eight sites in the UK.

Researchers will be looking for adverse reactions and the immune system responses to these new combinations of vaccines. The trial is not designed to show if the vaccines are effective at preventing disease and the University of Oxford has said the intent of the study is to show that mixing is not substantially worse than not mixing.

The Com-Cov study remit reads: “The purpose of this trial is to see how well people’s immune systems respond when their second ‘boost’ dose is a different type of vaccine to their first “prime” dose.

We will also be looking at how common vaccine reactions, such as fever, are after such ‘mixed’ schedules. This is important, as being able to use different vaccines in this way creates a more flexible immunisation programme; potentially allowing more people to be immunised more quickly. The researchers said they are enrolling people from all ethnicities and would particularly welcome participants from ethnic minority communities, considered among the higher-risk groups affected by Covid-19.