Experimental Covid-19 vaccine is put to its biggest test
The biggest test yet of an experimental Covid-19 vaccine got underway in the US on Monday with the first of some 30,000 Americans rolling up their sleeves to take part.
Final-stage testing of the vaccine, developed by the National Institutes of Health (NIH) and Moderna Inc, began with volunteers at numerous sites around the US given either a real dose or a dummy without being told which.
