World Health Organisation (WHO) chief Tedros Adhanom Ghebreyesus has said that the top health organisation has no guarantee whether any single Covid-19 vaccine now in development will work.

While addressing a virtual press conference, the WHO chief said: "We have no guarantee that any single vaccine now in development will work."

"The more candidates we test, the higher the chance we will have of a safe and efficacious vaccine," he added.

According to the WHO, almost 200 vaccines for Covid-19 are currently in clinical and pre-clinical testing.

"The history of vaccine development tells us that some will fail, and some will succeed," Ghebreyesus said.

Also, the WHO, in collaboration with global vaccine alliance group Gavi and the Coalition for Epidemic Preparedness Innovations (CEPI), has launched a scheme COVAX.

The aim of the collaboration is to accelerate the development of Covid-19 vaccines and enable equitable access for every country in the world.

The COVAX Facility enables governments to spread the risk of vaccine development and ensure their populations can have early access to effective vaccines.

Even more importantly, the COVAX Facility is the mechanism that will enable a globally-coordinated rollout for the greatest possible impact.

The facility will help to bring the pandemic under control, save lives, accelerate economic recovery and ensure that the race for vaccines is a collaboration, not a contest, according to the WHO chief.

"The fastest route to ending the pandemic and accelerating the global economic recovery is to ensure some people are vaccinated in all countries, not all people in some countries," he noted.