A world-first study has launched in the UK with the aim of examining the safety and efficacy of mixing different vaccines for COVID-19 as part of a two-dose regimen.
Patients involved in the 13-month clinical study will receive different COVID-19 vaccines for one of their two doses.
The study, which has received £7m in UK government funding, will be the first in the world to evaluate whether different vaccines can be used safely and effectively for two-dose regimes.
In a statement, the Department of Health and Social Care said that the study participants could either receive AstraZeneca (AZ)/Oxford University’s vaccine for their first dose and Pfizer/BioNTech’s vaccine for the second, or vice versa.
The Pfizer/BioNTech vaccine was the first COVID-19 vaccine to be granted authorisation for emergency use in the UK in December 2020.
Authorisation of AZ/Oxford’s vaccine closely followed, with the first person in the UK receiving the vaccine in early January.
As of 3 February, over ten million people in the UK had received the first dose of a COVID-19 vaccine, with close to half a million (498,962) having also received their second dose.
Results from the new mixed-vaccine study, known as Com-Cov, could make a case for the use of different vaccines to bolster the UK’s vaccine drive further.
“Given the inevitable challenges of immunising large numbers of the population against COVID-19 and potential global supply constraints, there are definite advantages to having data that could support a more flexible immunisation programme, if needed,” said Jonathan Van-Tam, deputy chief medical officer and senior responsible officer for the study.
Van-Tam added that combining vaccines could even enhance immune responses, by inducing “even higher antibody levels that last longer”.
The study will initially contain eight groups testing eight different combinations, with changes in vaccine dose order and time between doses.
It will be led by the UK’s National Immunisation Schedule Evaluation Consortium (NISEC) across eight National Institute for Health Research (NIHR) supported sites.
In addition to examining the safety and effectiveness of mixing different vaccines, researchers will also seek to gather immunological evidence on different intervals between vaccine doses for mixed-vaccine regimens compared to control groups using the same vaccine for both doses.
The DHSC added that initial findings from the Com-Cov study are expected to be released in the summer – if the study is successful, the government may then consider reviewing the current vaccine approach.
Currently, the UK is implementing a same-dose regimen for the national COVID-19 vaccine drive, with no plans at the moment to make changes to the programme.
“This is a hugely important clinical trial that will provide us with more vital evidence on the safety of these vaccines when used in different ways,” said Nadhim Zahawi, Minister for COVID-19 Vaccine Deployment.
“Nothing will be approved for use more widely than the study, or as part of our vaccine deployment programme, until researchers and the regulator are absolutely confident the approach is safe and effective,” he added.