The UK is undertaking the world’s first clinical trial that aims to determine the safety and effects of using different vaccines for the first and second dose.
The COVID-19 Heterologous Prime Boost study (or ‘Com-Cov’), which is backed by £7m of government funding and run by the National Immunisation Schedule Evaluation Consortium (NISEC) across eight National Institute for Health Research (NIHR) supported sites, will explore using the Oxford University/AstraZeneca COVID-19 vaccine for the first dose, followed by Pfizer/BioNTech’s vaccine for the second, for example.
It will take place across eight different sites across England – including in London, Birmingham, and Liverpool – and 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.
Dosing regimens and immune responses
Currently, a ‘same-dose regimen’ is used for the UK’s COVID-19 vaccination programme with no plans to change this, meaning that anyone who has received either the Pfizer or AstraZeneca vaccination will not be affected by this study.
The study will be carried out over 13 months and will monitor the impact of the different dosing regimens on patients’ immune responses, which have the potential to be higher or lower than from the same dose regimen.
Minister for COVID-19 Vaccine Deployment, Nadhim Zahawi, said: “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. 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.
“This is another great step forward for British science, expertise and innovation, backed by government funding – and I look forward to seeing what it produces.”
The study will initially have eight different arms testing eight different combinations, but more products may be added. These include:
- Two doses of the Oxford/AstraZeneca vaccine at 28 days apart
- Two doses of the Oxford/AstraZeneca vaccine at 12 weeks apart – as a control group
- Two doses of the Pfizer/BioNTech vaccine at 28 days apart
- Two doses of the Pfizer/BioNTech vaccine at 12 weeks apart – as a control group
- The Oxford/AstraZeneca vaccine for the first dose, followed by the Pfizer/BioNTech vaccine for the second, at 28 days apart
- The Oxford/AstraZeneca vaccine for the first dose, followed by the Pfizer/BioNTech vaccine for the second, at 12 weeks apart
- The Pfizer/BioNTech vaccine for the first dose, followed by the Oxford/AstraZeneca vaccine for the second, at 28 days apart
- The Pfizer/BioNTech vaccine for the first dose, followed by the Oxford/AstraZeneca vaccine for the second, at 12 weeks apart
The UK public can volunteer to be contacted about taking part in the study and further vaccine studies by joining the registry.
