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Com-COV 3 Study Starts Third Dose COVID-19 Vaccine Trial in 12-15-Year-Olds

Options for a third dose or 'booster' COVID-19 vaccine in 12- to 15-year-olds are to be tested in the Com-COV 3 vaccine study, launched today, according to researchers leading the work from Oxford University.

Designed to test reactogenicity (expected adverse reactions in response to vaccination) and immunogenicity to a variety of vaccines and dose options in young people, the third dose will be administered to those who have already been immunised with two doses of Pfizer-BioNTech vaccine.

Options include a further full adult dose of Pfizer-BioNTech vaccine (30 mcg); a one-third adult dose of Pfizer-BioNTech vaccine (10 mcg); a full child dose of Pfizer-BioNTech vaccine (10 mcg); a full dose of the Novavax vaccine; and the meningitis vaccine, followed by a dose of the Pfizer-BioNTech COVID-19 vaccine later in the study (serving as a control group).

The study, which is part of the COVID-19 Heterologous Prime Boost study (Com-Cov study programme) builds on from previous Com-COV and COV-BOOST studies, which have directly informed use of mixed COVID-19 vaccine schedules both in the UK and abroad. These studies have included teenagers receiving the first two vaccine doses.

"A key question for teenagers now is how well they respond to different options for a third dose of vaccine. This includes giving a lower dose of the Pfizer-BioNTech vaccine, or a protein-based vaccine produced by Novavax," said Matthew Snape, professor in paediatrics and vaccinology at the University of Oxford, and chief investigator of the trial.

"If these can be shown to produce a strong immune response with fewer temporary side effects, then this could improve the acceptability and uptake of a third dose adolescent campaign, both in the UK and internationally."

Participants will be randomised to receive either a full adult dose, one-third adult dose or full child dose of the Pfizer-BioNTech vaccine, or a full dose of the Novavax vaccine, while the control group will receive a meningitis vaccine (Bexsero, against MenB bacteria) followed by a Pfizer-BioNTech COVID-19 vaccine later in the study. 

As a single-blind study, participants will not know which third dose vaccine they receive until 3 months after the dose is given. The researchers will monitor reactogenicity and immunogenicity to the various combinations of vaccines, and they will also compare a one third adult dose of the Pfizer biotech vaccine to a full child dose of the same vaccine.

To date, the National Immunisation Schedule Evaluation Consortium (NISEC) COVID vaccine studies have enrolled more than 12,000 participants in the UK, with findings informing vaccination policy. This Com-COV 3 study in 12- to 15-year-olds aims to enrol 380 volunteers and will run across nine NIHR-supported sites plus one Health and Care Research Wales site.

Earlier results of the Com-COV 3 study in adolescents showed that fewer temporary side effects were observed with a reduced dose of the Pfizer/BioNTech vaccine as a second dose, while still generating a robust immune response. "This new stage of the Com-COV 3 study is the next step in this programme," said Prof Snape.

Dr Jakob Cramer, director of clinical development, Vaccine R&D, Coalition for Epidemic Preparedness Innovations (CEPI), said: "Clinical research on mix-and-match and fractional dose vaccination strategies have provided very relevant evidence on pragmatic recommendations on vaccine use in both high-income countries and low- and middle-income country settings.

"However, gaps remain in our understanding of the impact of such approaches for booster doses in under 15s – a group that accounts for around a quarter of the world’s population. The key additional evidence supplied through Com-COV 3 could help guide global vaccination programmes and ensure as many people as possible be protected from this dreadful disease."

COVID-19 Third (and Fourth) Dose Campaigns

In the UK, as of 25 May, just under 40,000,000 people have received a third dose (booster) COVID-19 vaccine, according to data on the UK government website. Everyone aged 5 and over could get a first and second dose of the COVID-19 vaccine, while people aged 16 and over, and certain children aged 12-15, can already get a third dose dose too.

Currently, fourth doses are only available to over-75s, residents of care homes for older people, and those over 12 years who have a weakened immune system. Young people under 18 years are currently only offered the Pfizer/BioNTech vaccine, and those under 40 years usually receive the Moderna or Pfizer/BioNTech.

Others outside of these categories can receive any of the vaccines approved for use in the UK. Most people receive the same vaccine for the first and second doses unless someone experiences side effects after the first dose, and most people are offered a third dose of the Pfizer/BioNTech or Moderna vaccines.  

The Com-COV 3 study is commissioned through the NIHR and backed by £2.8 million government funding, with support from both the Vaccine Taskforce and NIHR.

Initial results should be reported in 2022, after which the UK’s regulatory body, the Medicines and Healthcare products Regulatory Agency (MHRA) will assess the safety and efficacy of any new vaccine before considering market authorisation and subsequent rollout to patients.

The Joint Committee on Vaccination and Immunisation (JCVI) will also assess the evidence and make a recommendation.

The Com-COV 3 study is funded entirely by the Coalition for Epidemic Preparedness Innovations (CEPI).

Lead Image Credit: Andrej Ivanov/AFP via Getty Images