Australia said on Friday that it had ordered more alternatives to the AstraZeneca vaccine, delayed the vaccination launch, and Hong Kong was delaying the delivery of the injections amid concerns about the possible risk of very small blood clots.

The country’s decision to effectively finance its entire population vaccination plan by the end of October, highlights the complex public health balancing act the problem has created.

Millions of injectable doses of AstraZeneca have been administered safely worldwide and millions more have been ordered but several countries have restricted their use to older age groups as a precautionary measure while cases of freezing are being investigated.

Read also | Hong Kong suspended AstraZeneca’s jab orders

Australia says it has doubled the order of Pfizer injections after health authorities recommended that those under 50 take it instead of AstraZeneca, which has been a mainstay of the vaccination program.

“It is not an AstraZeneca vaccine ban,” Prime Minister Scott Morrison told reporters in Canberra. “For those over 50 years of age, there is a strong urge to use the AstraZeneca vaccine.”

The Anglo-Swedish company said it respects Australian recommendations and is working with regulators around the world “to understand the individual case, epidemiology and possible mechanisms that could explain this extremely rare event”.

European and British medicine regulators said this week they had found a possible link to an extremely rare case of brain blood clots, while firmly reiterating the importance of vaccines in mass vaccination against COVID-19.

The European Medicines Agency (EMA) received reports of 169 rare cases of brain blood clots in early April, after 34 million doses had been given, Sabine Straus, chair of the EMA’s safety committee, said this week.

Most of the cases reported were in women under 60 years of age.

On Friday, the EMA said that if a causal relationship is confirmed or deemed possible, regulatory action will be needed to minimize risks. He also said he was investigating Johnson & Johnson’s shot over reports of blood clots.

AstraZeneca’s injection is by far the cheapest and highest volume vaccine launched so far, making it perhaps the center of many of the inoculation programs around the world critical to curbing the global pandemic and preventing destructive lockdowns.

Germany, one of several European countries that has recommended alternatives to AstraZeneca for people under 60, said on Friday that a surge in infections meant a new lockdown was needed.

“Every day that we don’t act, we lose our lives,” said Lothar Wieler, president of the Robert Koch Institute.

Global supply

Hong Kong Health Secretary Sophia Chan said the city would postpone shipments of the AstraZeneca vaccine it has ordered this year to avoid shortages in other countries.

“We believe that the AstraZeneca vaccine does not need to be supplied to Hong Kong this year, so as not to cause waste when global vaccine supplies are still limited,” he said.

The government is considering buying a new type of vaccine that might offer better protection, he added.

The Chinese-ruled city has ordered 7.5 million doses of AstraZeneca, which is scheduled to arrive in the second half of 2021. But Chan said the global financial hub has ample alternatives.

Costa Rica said on Thursday they would use AstraZeneca’s fire after assessing EMA’s guidance.

More than 40,000 doses of vaccine arrived in the country on Wednesday, the first shipment under a deal for one million vaccines under the World Health Organization’s (WHO) COVAX mechanism and the GAVI alliance to ensure vaccines reach poorer states.

All countries that recommend age limits have emphasized that the vaccine is effective and that the benefits far outweigh the risk of contracting COVID-19 for the elderly.

France’s leading health agency, where vaccine hesitation is high, recommended on Friday that those over 55 who had received the first dose of AstraZeneca’s injection be given an alternative to the second.

Haute Autorite de la Sante suggested they get a new style messenger-RNA vaccine, confirming an earlier Reuters exclusive. Two such vaccines, one from Pfizer and BioNTech and one from Moderna, have been approved for use in France.

The Messenger RNA vaccine prompts the human body to make a protein that mimics a part of the virus, triggering an immune response. AstraZeneca injections generate an immune response using a harmless, weakened version of the common chimpanzee flu virus.

The French health agency also said there should be an interval of 12 weeks between two injections in such cases and recommended studies to assess the immune response provided by this mixed vaccine prescription.

(With input from the agency)