Australia has issued a worrying warning over the AstraZeneca vaccine, telling those under the age of 50 to not get the jab. It follows confirmation from the Australian Technical Advisory Group on Immunisation (ATAGI) that the vaccine may cause extremely rare but potentially deadly blood clots.

In a press conference on Thursday evening, the Australian government said the Pfizer vaccine will now be the preferred jab for under 50s. Under Australia’s vaccine strategy, most Australians were expected to the receive the AstraZeneca shot. However, it looks like the government will now be forced to rely on the Pfizer jab, which is imported from overseas, and the yet-to-be-approved Novavax vaccine to complete the roll out.

“At the current time, the use of the Pfizer vaccine is preferred over the AstraZeneca vaccine in adults aged less than 50 years who have not already received the first dose of AstraZeneca vaccine,” Australia’s Chief Medical Officer Paul Kelly said.

“This is based both on the increased risk of complications from Covid-19 with increasing age and thus increased benefit of the vaccination and the potentially lower but not zero risk of this rare event with increasing age.”

He went on to say that the AstraZeneca vaccine should only be given to adults under 50 years of age “where benefit clearly outweighs the risk for that individual’s circumstances”. Meanwhile, people who have already had their first dose of the vaccine without any serious adverse reaction can safely be given a second dose.

“So it’s very important that those people in those priority groups are vaccinated as quickly as possible and AstraZeneca is perfectly safe in people in those older age groups,” Professor Kelly said.

Prime Minister Scott Morrison reassured Aussies the government was taking the best possible approach based on the medical advice given.

“We’ve been taking the necessary precautions based on the best possible medical advice,” he said. “We have always taken the time to ensure we get that ­advice, consider it carefully, and make decisions in the best interests of Australians and those best interests, principally, have to address the health of Australians.”

It comes after the European Medicines Agency (EMA) found a possible link between AstraZeneca’s Covid-19 vaccine and rare blood clotting issues in adults but concluded the risk of dying from Covid-19 is far greater than dying from complications caused by the vaccine.

In the wake of the EMA’s findings, the United Kingdom’s vaccine advisory board said all people under 30 will now be offered alternative vaccines such as Pfizer and Moderna. The Joint Committee on Vaccines and Immunisation said there had been 79 reported cases of blood clots in the UK, out of more than 20 million doses of the AstraZeneca vaccine administered, 19 have died.

Several European nations including France, Italy and Germany, Ireland, Netherlands, Denmark, Norway, Iceland and Bulgaria, have already suspended use of the vaccine over its link to blood clots. Denmark was one of the first countries to suspend the vaccine in early March, after the death of a 60-year-old woman, with Nationals Senator Matt Canavan calling for Australia to follow Demark’s lead.

On March 29, Canada suspended the use of the AstraZeneca vaccine for people under 55. The pause came following a recommendation by the country’s National Advisory Committee on Immunization (NACI) with Dr Shelley Deeks, vice-chair of NACI, saying that given the risks there was “substantial uncertainty” about the benefit of providing the vaccine to those under 55.