The UK medicines regulator has approved the use of Pfizer and AstraZeneca as Covid booster vaccines, paving the way for a rollout ahead of the winter. But the Joint Committee on Vaccination and Immunisation (JCVI), the UK vaccine advisory body, has not decided if they are needed, and who should be eligible. The JCVI has said a third dose should be offered to people with severely weakened immune systems. Up to half a million people over the age of 12 in the UK are in this group. A separate booster programme against Covid-19 would aim to extend protection for millions more at high risk from the virus, although there is disagreement over whether this is really necessary.