The rush to immunise populations against Covid-19 could lead to the rollout of a vaccine that is not very effective and risk worsening the pandemic, leading scientists have said.
Politicians and commercial companies are competing to be the first to license a vaccine, but experts say the world would be better served by waiting until comprehensive results showed at least 30-50% effectiveness.
Ministers announced on Friday that the UK would take emergency powers to push any vaccine through the regulatory processes with unprecedented speed before the end of the year. Donald Trump wants to be able to announce the US has a vaccine before tthe presidential election on 3 November.