World faces around 4,000 COVID-19 variants as Britain explores mixed vaccine shots
A dose of Oxford-AstraZeneca COVID-19 vaccine is prepared by a member of the Hampshire Fire and Rescue Service at Basingstoke Fire Station, in Basingstoke, Britain Feb. 4, 2021. PHOTO BY ANDREW MATTHEWS /Pool via REUTERS LONDON — The world faces around 4,000 variants of the virus that causes COVID-19, prompting a race to improve vaccines, Britain said…