The WHO welcomed the new front in the fight against the virus -- but also said it wanted to see the data behind the vaccines, to assess whether to aprove them. China on Sunday launched the world’s first inhalable Covid vaccine, Convidecia Air, which is made by CanSino Biologics and administered through a nebuliser.

And India approved a nasally-administered Covid-19 vaccine for emergency use on Tuesday, developed by Bharat Biotech.

WHO emergencies director Mike Ryan said nasal vaccines generated immune response in the respiratory mucosa in the lungs. "You’re generating the first line of defence at where the virus enters and causes a lot of damage," he explained.

In doing so, nasal vaccines could potentially prevent a person from being infected and passing the virus on. That opportunity to reduce both the severity of infection and onward transmission "may offer us a much stronger prospect of control of Covid in the long run", he told a press conference.