A group of 6 to 17-year-olds will test the jab to see how effective it is on them.
This new clinical trial will enrol 300 volunteers, with up to 240 of these volunteers receiving the Oxford/AstraZeneca vaccine and the remainder a control meningitis vaccine.
This has been shown to be safe in children but is expected to produce similar reactions, such as a sore arm.
The University of Oxford said theirs was the first trial in the 6-17 age group. It said other trials had begun but only measuring efficacy in those aged 16 and 17.
Andrew Pollard, Professor of Paediatric Infection and Immunity, and Chief Investigator on the Oxford vaccine trial, said:
"While most children are relatively unaffected by coronavirus and are unlikely to become unwell with the infection, it is important to establish the safety and immune response to the vaccine in children and young people as some children may benefit from vaccination.
"These new trials will extend our understanding of control of SARS-CoV2 to younger age groups."
Earlier this week, England’s deputy chief medical officer said “several” trials were under way to develop vaccines that are safe and effective in children.
Rinn Song, Paediatrician and Clinician-Scientist, Oxford Vaccine Group, said:
"The COVID-19 pandemic has had a profound negative impact on the education, social development and emotional well-being of children and adolescents, beyond illness and rare severe disease presentations.
"It is therefore important to collect data on the safety and the immune response to our coronavirus vaccine in these age groups, so that they could potentially benefit from inclusion in vaccination programs in the near future."
The University of Oxford, together with three partner sites in London, Southampton and Bristol, is launching the trial today with first vaccinations expected during February.