US government scientist Anthony Fauci has said the coronavirus vaccine “cavalry” is coming but urged the public not to let down its guard, and called for a stronger WHO to ward off future pandemics.

Fauci, a world-leading expert on infectious diseases who has been at serious odds with President Donald Trump over Covid-19, said that after Pfizer's vaccine, another is “literally on the threshold of being announced”.

Moderna, which is co-developing its vaccine candidate with the US National Institutes of Health, says it is close to reaching a threshold in trials to apply for an emergency use authorisation from US regulators.

“Help is on the way, but it isn't here yet,” he said, urging the public to respect public health measures such as wearing masks and washing hands.