As coronavirus vaccines hurtle through development, scientists are getting their first look at data that hint at how well different vaccines are likely to work. The picture, so far, is murky.

On 18 May, US biotech firm Moderna revealed the first data from a human trial: its COVID-19 vaccine triggered an immune response in people, and protected mice from lung infections with the coronavirus SARS-CoV-2. The results — which the company, based in Cambridge, Massachusetts, announced in a a press release — were widely interpreted as positive and sent stock prices surging. But some scientists say that because the data haven’t been published, they lack the details needed to properly evaluate those claims.