The U.K. is on track to vaccinate all people over age 50 by May and is already planning for a program of top-up immunizations to fight new variants of coronavirus from the autumn, officials said.

Health Minister Nadhim Zahawi predicted annual vaccination drives similar to the program of injections given for influenza each year.

Work is already underway to develop a shot that will offer better protection against the South Africa variant, after a study suggested the Oxford University-AstraZeneca vaccine had limited effect on mild COVID-19.