As some governments and pharmaceutical officials prepare for Covid-19 booster shots targeting more infectious virus variants, health authorities say it’s too early to tell if they will be required.

“We do not have the information that’s necessary to make the recommendation on whether or not a booster will be needed,” said Soumya Swaminathan, the World Health Organisation’s (WHO) chief scientist. The “science is still evolving”.

Such a call is “premature” while high-risk individuals in most of the world haven’t yet completed a first course of vaccination, she said. Data from countries introducing precautionary extra inoculations later this year, particularly for vulnerable people whose immunity to SARS-CoV-2 may wane faster, will inform WHO’s guidance, Swaminathan added...