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COVID-19 vaccine lower booster dose study launches across UK

Cov-Boost Fractional Dose Study Recruiting

Published: 18 January 2022

Over 900 young people from across the UK are set to receive a third COVID-19 vaccine booster at a lower dose than in adults, through the COV-BOOST study.

The COV-BOOST: Young Adults Fractional Dosing Sub-study, will be run at 13 NIHR-supported research sites in England, and a site in Wales, and is being led by University Hospital Southampton NHS Foundation Trust.

Young adults have a stronger immune response to vaccines than older adults.Results from COVID-19 vaccine studies have suggested lower doses of the Pfizer or Moderna COVID-19 vaccines may give as good an immune response in young adults as higher doses. Lower doses may also be linked with fewer side effects or lower rates of already rare adverse events.

Using lower doses could allow existing stocks of vaccines to be given to more people, which is important while the need for vaccines is greater than the number of doses available globally.

Participants to the COV-BOOST study will be randomly selected to receive one of the following doses:

- A single dose of Pfizer (currently used in the UK booster programme)
- One third of a single Pfizer dose (currently recommended for 5 - 11 years old in the UK)
- A half Moderna dose (currently used by the NHS as a 3rd dose booster)
- One quarter of a single Moderna dose

The NIHR-supported study is looking for volunteers who are:

- between 18 to 30 years old
- have had two doses of the Pfizer or Moderna COVID-19 vaccines, with at least 3 months (84 days) since their second dose
- have not received a booster

People who have tested positive for COVID-19 in the past, and have had their second vaccine, can also take part in the study.

All participants will be monitored throughout the study for any potential side effects and will have bloods taken to measure their immune responses on the day of their first visit and then two weeks, one month, three months and eight months following vaccination.

The COV-BOOST study published its full initial results in the Lancet in December 2021, which found several COVID-19 vaccines were safe and boosted immunity and its early findings in September 2021 informed the UK’s booster programme.

Professor Saul Faust, Chief Investigator and Director of NIHR Southampton Clinical Research Facility, said:

“If we find that giving a lower dose of these vaccines to young adults gives as good an immune response as a higher dose, this could have positive implications for global vaccine supply and may result in a lower side effect profile in this age group. 

“Our vital COVID-19 vaccine research would not be possible without support from the public, who continue to step forward to take part in our studies. We need young adults from all backgrounds to take part in this new study and I would encourage anyone interested to visit the COV-BOOST website to find out more and sign up.”

Professor Andrew Ustianowski, National Clinical Lead for the UK NIHR COVID Vaccine Research Programme, said:

"The COV-BOOST study has already provided the UK and other countries with extremely valuable data when it comes to understanding how we can boost populations and protect them against COVID-19. The latest phase of the study could also prove very useful and help identify if lower doses can be as effective whilst having other specific advantages

"We cannot thank participants enough for their commitment to COVID-19 vaccine studies and encourage those who have not yet received a booster to sign up for this study.

“The UK research community and public have played a huge role working with the NHS and NIHR supported teams to identify several important COVID-19 treatments and vaccines over the last two years. This latest booster sub-study can build upon our strong vaccine data and likely help us find more efficient ways to use vaccine supplies."

Anyone interested in finding out more or taking part in the study can visit the COV-BOOST website, where they can complete the study questionnaire to see if they are eligible.

Participants will be reimbursed for their time, inconvenience and travel, with boosters given in January and February.

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