UK health authorities said COVID-19 booster shots could restore protection against mild disease caused by the Omicron variant. Dr Susan Hopkins, chief medical adviser for the UK Health Security Agency, said vaccine effectiveness dropped significantly three months after the first two doses. But she noted that the vaccine's protective impact could be partially restored by booster shots. Real-world analysis has shown the Omicron strain can evade vaccines. The agency also said it expected Omicron to be the dominant variant in the UK by mid-December.