The Oxford/AstraZeneca vaccine is linked to rare blood clots. Photo: Russell Cheyne/AFP

The Hong Kong government has been urged by several medical experts to scrap the order of AstraZeneca vaccines after the European Medicines Agency said blood clots could be a rare side-effect.

Government advisor on the pandemic David Hui Shu-cheong said the city has a sufficient supply of Sinovac and BioNTech vaccines for now.

Hui, chairman of the Department of Medicine and Therapeutics at The Chinese University of Hong Kong, said the government should instead look to order second-generation vaccines.

Apart from growing concerns over the AstraZeneca vaccine’s safety in Europe, the jab’s lower effectiveness against the South African strain is also undesirable, Hui said.

He understood that it is still possible to scrap the order for 7.5 million AstraZeneca doses as the Hong Kong government has only entered into an initial agreement with the maker. The Johnson & Johnson vaccine was a good choice.

On Wednesday, the European Medicines Agency (EMA) said it was investigating links between the vaccine and a rare blood clot. It said unusual blood clots should be listed as a very rare, possible side-effect of the AstraZeneca jab.

EMA executive director Emer Cooke said the vaccine’s benefits still outweigh the risks as “the risk of mortality from Covid is much greater than the risk of mortality from these rare side effects.”

On the same day, Britain’s Joint Committee on Vaccination and Immunization said people under 30 should be offered an alternative vaccine such as the Moderna or BioNTech one if available. So far, nearly 37 million Covid-19 vaccine doses have been administered in the UK, about 20 million of which have been AstraZeneca.

Meanwhile, the World Health Organization said it’s unlikely to change its guidance that the benefits of AstraZeneca outweigh any risk.

Some scientists suggested that the AstraZeneca vaccine triggered an unusual antibody in some cases.

The blood clots might be linked to the widespread use of oral contraceptives among young women in Europe, as birth control pills could also cause blood clots, said William Chui from the Society of Hospital Pharmacists. The Hong Kong government should slash half of the original order of 7.5 million doses of AstraZeneca vaccine if it could not cancel the entire order, Chui said.

Chui said the Johnson & Johnson vaccine is a better choice due to its higher protection rate against the South African strain.

In Europe, 83 people have developed blood clots getting the AstraZeneca jabs and 24 of them died, said Ho Pak-leung, head of the University of Hong Kong’s Center for Infection.

Hong Kong authorities should cancel the AstraZeneca order due to the safety concerns, Ho said, adding that there’s no evidence that the vaccine is any better than the Sinovac and BioNTech ones on offer in the territory.

Ho suggested that the government purchases more BioNTech jabs, instead of the Johnson & Johnson one, which is also viral vector-based like AstraZeneca. He warned that problems such as rare blood blots could also emerge from the Johnson & Johnson vaccine.

There are four types of Covid-19 vaccine, including the inactivated (or whole virus), mRNA (nucleic acid), viral vector and protein subunit vaccines. China’s Sinovac and Sinopharm vaccines are made of inactivated virus while BioNTech’s one is a nucleic acid vaccine. Both AstraZeneca and Johnson & Johnson vaccines are viral vector-based while the Novavax jab contains protein subunits.

Last month, the European Union said it had approved four vaccines, including BioNTech, Moderna, AstraZeneca and Johnson & Johnson, for its coming vaccine passport scheme.

A nurse holds her arm after receiving the Sinovac vaccine in Hong Kong. Photo: Peter Parks/AFP

Hong Kong’s Food and Health Bureau said it would continue to collect information about the safety issues of different vaccines from health regulators and drug manufacturers. It said it had not received an approval application from AstraZeneca for the use of its vaccine in Hong Kong. It would not disclose its agreements with drug suppliers.

On Thursday, AstraZeneca said its schedule to supply Hong Kong and Macau had not changed. It said it was investigating each of the blood clotting cases and trying to find out why they happened.

As of Wednesday, Hong Kong has administered more than 659,600 doses of Covid vaccine. About 516,000 people have received their first dose, with 336,200 people receiving the Sinovac vaccine and 179,800 getting the BioNTech one. About 143,600 people have had their second dose, with 104,100 people receiving the Sinovac vaccine and about 39,500 people getting the BioNTech shot.

On March 10, a family of three planned to receive the Sinovac vaccine in the Tin Shui Wai Sports Centre but they mistakenly went to the Yuen Long Sports Centre for the BioNTech jab. They later agreed to receive BioNTech vaccine for their second dose. Earlier, a man was injected with the Sinovac vaccine though he booked for the BioNTech one.

The government said it had urged the staff in vaccination centres to cross-check the identity of those who get vaccinated.

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