Vaccine makers prepare for game of Covid cat and mouse

Vaccine makers and medicine regulators are sketching out plans in case the mutating coronavirus turns vaccine development into a game of cat and mouse. Just weeks after leading manufacturers secured the first regulatory approvals, mutations in the virus have forced scientists to re-test their Covid-19 vaccines and prepare to tweak their formula should the shots prove less effective. At the same time, regulators are considering how they could fast-track new approvals and whether they could use the seasonal flu jab as a model to authorise revised versions without requiring long trials.