World faces around 4,000 COVID-19 variants as Britain explores mixed vaccine shots
LONDON (Reuters) - The world faces around 4,000 variants of the virus that causes COVID-19, prompting a race to improve vaccines, Britain said on Thursday, as researchers began to explore mixing doses of the Pfizer and AstraZeneca shots in a world first.
Thousands of variants have been documented as the virus mutates, including the so-called British, South African and Brazilian variants which appear to spread more swiftly than others.