The U.S. has doubled its investment to nearly US$1 billion for the development of an effective coronavirus vaccine by American firm Moderna, which on Monday begins the decisive final phase of clinical trials.
The government of the US now plans to spend up to $472 million on top of the previously announced $483 million, the Moderna biotechnology company announced Sunday.
According to AFP reports, Moderna said the added investment was justified by its decision, in conjunction with the government, to "significantly" expand a phase-three clinical trial of a candidate vaccine to include 30,000 participants.
In a small, initial trial, Moderna's experimental vaccine produced coronavirus antibodies which should help fend off the disease in the bodies of all 45 participants.
In the expanded trial starting Monday, half the 30,000 participants will receive a 100-microgram dose of the vaccine, while the rest will be given a placebo.
Moderna, which has been working with U.S. health authorities, said it expects to be able to produce 500 million doses a year and potentially up to 1 billion starting in 2021.
The U.S. has suffered more than 146,000 coronavirus deaths, leading the world in that grim category, even as the number of new cases has continued to surge.