FDA panel to advise on whether — and how — Covid vaccines should be updated

The Food and Drug Administration faces an important decision in coming days — whether to instruct companies that make Covid-19 vaccines to update the viral strain or strains of SARS-CoV-2 those products target.

It seems almost a given that the FDA will tell manufacturers that it is time to change the composition of Covid vaccines, with an eye to a rollout of updated vaccines to be administered in the autumn. But how and to what are questions that still need answering.