LONDON, Dec 24 (Reuters) - Britain said on Friday it would offer visas for care workers for a 12 month period after the coronavirus pandemic exacerbated staff shortages within the social care sector. The temporary measures were expected to come into effect early next year and would be in place for a minimum of 12 months, the government said. The minimum annual salary to qualify for the visa will be 20,480 pounds ($27,445). ($1 = 0.7462 pounds)