Britain is in talks with Oxford and AstraZeneca for additional doses of their Covid-19 vaccine that has been modified to better target the "beta" coronavirus variant first identified in South Africa, and it will fund trials of the shots.

Britain has previously secured 100 million doses of the vaccine, developed at the University of Oxford and licenced to AstraZeneca, and the health ministry said the extra doses under discussion would be tailored to target the B.1.351 variant.

South Africa put the use of AstraZeneca's shot on hold in February after...