Western governments rushed to offer support for the AstraZeneca Covid-19 vaccination after South Africa halted its roll-out when research showed it offered minimal protection against mild infection from a variant spreading there, according to Reuters.

The arrival of vaccines has given hope that scientists can tame a pandemic that has killed 2.3 million people worldwide. But if vaccines are less effective against new variants, they may need to be tweaked and people may need booster shots.

South Africa announced its pause after researchers from the University of Witwatersrand and the University of Oxford found that the AstraZeneca vaccine provided only minimal protection against mild or moderate infection from the B.1.351 variant, now the dominant form of the virus in that country.