BEIJING, Oct 27 (AFP) - The Chinese city of Shanghai started administering an inhalable COVID-19 vaccine on Wednesday (Oct 26) in what appears to be a world first.

The vaccine, a mist that is sucked in through the mouth, is being offered for free as a booster dose for previously vaccinated individuals, according to an announcement posted on an official city social media account.

Needle-free vaccines may persuade people who do not like getting a shot to get vaccinated, as well as help expand vaccination in poor countries because they are easier to administer.

China does not have vaccine mandates but wants more people to get booster shots before it relaxes strict pandemic restrictions that are holding back the economy and increasingly out of sync with the rest of the world.

A video by Shanghai Media Group showed people at a community health centre sticking the short nozzle of a translucent white cup into their mouths. A usage instruction at the health center asks people to inhale deeply until no aerosol is left in the cup and then to hold their breath for five seconds.

"It was like drinking a cup of milk tea," one Shanghai resident who gave his name only as Chen said. "When I breathed it in, it tasted a bit sweet."

A vaccine taken in the mouth could also fend off the virus before it reaches the rest of the respiratory system, though that would depend in part on the size of the droplets, one expert said.

Chinese regulators approved the vaccine for use as a booster in September.

It was developed by Chinese biopharmaceutical company CanSino Biologics as an aerosol version of the same company's one-shot adenovirus vaccine, which uses a relatively harmless cold virus.