The US regulator has found Moderna’s coronavirus vaccine to be safe and “highly effective”, clearing the way for a second jab to receive emergency use authorisation later this week.

The US Food and Drug Administration report on Moderna’s vaccine trials on Tuesday suggested that immunity starts about 10 days after the first of two injections, much like the one made by Pfizer and BioNTech, which received emergency use authorisation last week.

A second approval could significantly expand access to Covid-19 vaccines in the US, where the pandemic has now killed more than 300,000 people, according to Johns Hopkins University data. While the US government has been offering to help Pfizer expand manufacturing capacity, it secured another pre-order for 100m Moderna vaccines last week, bringing its total to 200m.