Administering multiple booster doses against COVID-19 is not sustainable in the longer term, international drug regulators said during a meeting of the International Coalition of Medicines Regulatory Authorities, held Jan. 12. Regulators argued that a long-term strategy should involve vaccines capable of tackling several variants at once, not just omicron, and that tweaking existing vaccines and comparing them with first-generation vaccines using clinical studies is the way forward, according to a report from the meeting.