mRNA vaccines were heralded as a medical marvel that saved lives during the Covid pandemic, but now the US is pulling back from researching them.
US Health Secretary Robert F Kennedy Jr has cancelled 22 projects - worth $500m (£376m) in funding – for tackling infections such as Covid and flu.
So does Kennedy - probably the country's most famous vaccine sceptic – have a point, or is he making a monumental miscalculation?
Prof Adam Finn, vaccine researcher at the University of Bristol, says "it's a bit of both" but ditching mRNA technology is "stupid" and potentially a "catastrophic error".
Let's unpick why.
