World’s First COVID-19 Vaccine Booster Study of Seven Vaccines to Provide Vital Data on Impact of Third Dose on Immune Response

A new government-funded clinical trial to look at different COVID-19 ‘booster’ vaccines has been launched in the UK and the initial results trialing seven vaccines are expected in September that will inform plans for a booster program.

Thousands of volunteers will receive a booster COVID-19 vaccine in the new Cov-Boost study, led by University Hospital Southampton NHS Foundation Trust (Southampton, UK) and backed by government funding through the Vaccines Taskforce. The study will trial seven vaccines and will be the first in the world to provide vital data on the impact of a third dose on patients’ immune responses. It will give scientists from around the globe and the experts behind the UK’s COVID-19 vaccination program a better idea of the impact of a booster dose of each vaccine in protecting individuals from the virus.


The trial will look at seven different COVID-19 vaccines as potential boosters, given at least 10 to 12 weeks after a second dose as part of the ongoing vaccination programme. One booster will be provided to each volunteer and could be a different brand to the one they were originally vaccinated with. Vaccines being trialed include Oxford/AstraZeneca, Pfizer/BioNTech, Moderna, Novavax, Valneva, Janssen and Curevac, as well as a control group.

The study will take place at 16 NIHR-supported sites across England, and also within Health and Care Research Wales and NHS Research Scotland sites. It will include a total of 2,886 patients and participants are to begin being vaccinated from early June. Participants will be adults aged 30 years or older as these will have been those immunized early on in the vaccination program - for example, adults aged 75 and over or health and care workers. All participants will be monitored throughout the study for any side effects and will have bloods taken to measure their immune responses at days 28, 84, 308 and 365, with a small number having additional blood tests at other times. All sites will have an electronic diary for all participants that will send alerts to the team in real time if needed and a 24-hour emergency phone to a doctor on the study, who can provide further clinical advice.

Earlier this year, the UK government had launched the ComCov clinical trial, which aims to determine the effects of using different vaccines for the first and second dose - for example, using Oxford/AstraZeneca’s vaccine for the first dose, followed by Pfizer/BioNTech’s vaccine for the second. Initial results from this trial have shown that mixing the doses slightly increases the frequency of mild-to-moderate symptoms following vaccination, but there were no serious outcomes. Further results from this clinical trial – including on the immune response in people who have two different vaccine doses – are expected over the coming months. The UK government is preparing for a booster program based on clinical need and the final policy will take into account the results of clinical trials.

“We will do everything we can to future-proof this country from pandemics and other threats to our health security, and the data from this world-first clinical trial will help shape the plans for our booster program later this year,” said British Health and Social Care Secretary, Matt Hancock. “I urge everyone who has had both doses of a COVID-19 vaccine, and is eligible, to sign up for this study and play a part in protecting the most vulnerable people in this country and around the world for months and years to come.”

Related Links:
University Hospital Southampton NHS Foundation Trust