Dr Anthony Fauci has expressed his optimism that a Covid-19 vaccine would be ready by the end of the year.
Speaking to US House of Representatives on Friday he said that they are cautiously optimistic whilst expressing scepticism at the vaccine efforts of Russia and China.
He said while the effectiveness of a trial is not guaranteed he was hopeful that by late fall and early winter, a safe and effective vaccine would be found.
Vaccine trials are continuing across the world with governments pledging billions. Some have entered late stage human trials but they still require rounds of testing.