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Call for Southampton over 50s to be part of coronavirus vaccine dose gap study

Updated: Feb 19, 2021

Southampton doctors are calling for volunteers over the age of 50 to take part in a study looking at the impact of varying the time between doses, and using different coronavirus vaccines for first and second doses.

The trial will compare peoples’ immune response to booster injections at either 28 days or 12 weeks after their first dose. These intervals will be tested using the Oxford/AstraZeneca and Pfizer/BioNTech vaccines currently being rolled out across the NHS, and also in mixed dosing – using one vaccine for the first dose and the other for the second.

“This trial will provide vital data for all our reassurance about the current NHS vaccine roll out, and for how we use COVID-19 vaccines in the future,” said Professor Saul Faust, Director of the NIHR Southampton CRF, who is leading the trial locally.

Volunteers needed

The study will be run in the NIHR Southampton Clinical Research Facility (CRF) at University Hospital Southampton, aiming to recruit 100 volunteers aged 50-years-old and above. They will join 700 others at seven further sites nationally in the study referred to as the COVID-19 Heterologous Prime Boost study, or ‘Com-Cov’.

Anyone from Southampton or Hampshire and Isle of Wight wanting to take part can register online at

“The people of our city and region contributed massively to the trials that got these vaccines to the front line – we’re hoping they will come forward again to help us use the vaccines as effectively as possible. We’re really keen to hear from those between 50 and 70 years of age, especially those from a black or Asian background. No one taking part will receive a placebo, or dummy, dose – all receive two doses of the currently approved vaccines used by the NHS.”

Comparing dose type and timing

The study will test eight different combinations and interval doses for the Oxford/AstraZeneca and Pfizer/BioNTech vaccines. It will compare two doses of the same vaccine against one dose of each vaccine, with either the Oxford/AstraZeneca or Pfizer/BioNTech vaccine as the first dose. For each combination, the researchers will compare giving the two doses 28 days or 12 weeks apart.

Undertaken by the National Immunisation Schedule Evaluation Consortium (NISEC) and the Oxford Vaccine Group, the study is backed by £7 million of government funding from the Vaccines Taskforce. It has received ethics approval, as well as approval from the Medicines and Healthcare products Regulatory Agency (MHRA) to commence.

Vaccinations are expected to start towards the middle of February, with initial results to be made available over the summer period. The study will last for 13 months.

If the study shows promising results, the MHRA would formally assess the safety and efficacy of any new vaccination regimen before it would be rolled out to patients.

Those interested in volunteering at Southampton can find out more by visiting

The UK public can continue to support the national effort to speed up vaccine research and receive more information about volunteering for future vaccine studies by


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