Hong Kong on Friday confirmed it has requested AstraZeneca suspend delivery of its Covid-19 vaccine amid fears of severe side effects and concerns over its efficacy against new variants of the coronavirus.

Europe's medicines regulator said this week the AstraZeneca vaccine could cause very rare blood clots in some recipients, prompting a cascade of countries to pull the plug on giving it to people under a certain age.

Britain sought Thursday to quell fears over the jab, saying the potential side effects were extremely rare -- and the risk of falling seriously sick from Covid-19 was far greater.

On Friday Hong Kong's health chief Sophia Chan said the city has asked AstraZeneca not to deliver as planned later this year.

"We think it is not necessary for AstraZeneca to deliver the vaccines to the city within this year," she said, adding Hong Kong wanted "to avoid any waste as vaccines are in short supply globally".

Wealthy Hong Kong has already secured a good supply of vaccines for its 7.5 million residents.

It has signed deals for 7.5 million shots each with BioNTech/Pfizer and China's Sinovac, both of which have begun deliveries.

Europe's medicines regulator said this week the AstraZeneca vaccine could cause very rare blood clots in some recipients
The AstraZeneca COVID vaccine is pictured. AFP / JOEL SAGET

Chan said Hong Kong was also keen to look at other vaccines that may have stronger results against newer strains of the coronavirus.

Earlier this week David Hui, a leading public health expert and government adviser, called for Hong Kong to replace AstraZeneca with a new single dose vaccine made by Johnson and Johnson.

Densely populated Hong Kong was one of the first places to be hit by the coronavirus, but strict social distancing and universal mask wearing have helped keep infections to just over 11,000 with 205 deaths.

While it has a steady supply of vaccines, take up has been slow amid swirling distrust of the government as Beijing cracks down on democracy supporters.

So far just 529,000 people have had their first dose.

Public confidence has also been hampered by government messaging.

China's Sinovac received fast-track approval despite not publishing its clinical trial data in a peer reviewed journal.

Administration of BioNTech's vaccine was also briefly suspended after some vials were found to be defective even though authorities said any damaged bottles were discarded before being used in vaccinations.

Coronavirus