AstraZeneca and the University of Oxford on Sunday began new trials to test a modified vaccine against the Beta variant, which first emerged in South Africa, news agency AFP has reported.
The new vaccine has been designed using the same base as the main AstraZeneca shot but with minor genetic alterations to the spike protein based on the Beta variant.
The 'booster' vaccine's trial will involve around 2,250 participants from Britain, South Africa, Brazil and Poland.
Initial data from the trial is expected later this year.
"Testing booster doses of existing vaccines and new variant vaccines is important to ensure we are best prepared to stay ahead of the pandemic," the Oxford Vaccine Group said.