Russia's claim that it has developed the world's first vaccine met with scepticism about its effectiveness, as New Zealand warned the re-emergence of COVID-19 could delay its upcoming election.
On Tuesday, Russia had claimed it had developed the world's first vaccine offering "sustainable immunity" against the coronavirus, despite mounting scepticism about its effectiveness.
President Vladimir Putin insisted the vaccine was safe and that one of his own daughters had received the inoculation, dubbed "Sputnik" after the pioneering 1950s Soviet satellite.
On a visit to Taiwan, US Health Secretary Alex Azar echoed such concerns.
"It's important that we provide safe, effective vaccines and that the data be transparent... This is not a race to be first," Azar told reporters during a conference call.
"I should note that two of the six US vaccines that we've invested in entered the phase three clinical trials weeks ago that the Russian vaccine is now only beginning," he added.
The WHO's spokesman in Geneva Tarik Jasarevic said it was in "close contact" with Russian health authorities but that it was too soon for the global health body to give its stamp of approval without a rigorous review.
The WHO says that 165 candidate vaccines are being worked on around the world, with six reaching Phase 3 clinical trials, the last step before regulatory approval.
On the other side of the world, New Zealand's Prime Minister Jacinda Ardern said the upcoming election in September could be postponed as the coronavirus seems to have re-entered the Pacific country.
With 1.5 million people under stay-at-home orders, and millions more at risk of a wider outbreak, Ardern said she was seeking advice on delaying the election currently scheduled for September 19. Parliament was due to be dissolved yesterday to allow the election to take place, but the centre-left leader held off the move until Monday to monitor how the crisis evolves.
With the number of coronavirus cases worldwide surpassing 20 million and the number of deaths fast approaching 750,000, the World Health Organization has warned that a second wave is "almost inevitable".
Countries across the globe are starting to reintroduce restrictions as the number of infections tick higher.
In Belgium, which is battling one of the most serious coronavirus outbreaks in Europe, authorities made the wearing of face masks in public compulsory in the Brussels region from Wednesday.
In Italy, too, regions have begun to order new quarantines for people returning from higher-risk European countries such as Spain as they hope to stem new outbreaks.