Australians under 50 are being advised against getting the AstraZeneca COVID jab, the bedrock of the nation’s vaccine rollout, after medical experts raised concern over blood clot issues overseas.

It comes from advice from the Australian Technical Advisory Group on Immunisation (ATAGI), which is still recommending AstraZeneca for those over 50.

In a snap press conference on Thursday night, Prime Minister Scott Morrison said the group had met for several hours earlier on Thursday and provided recommendations at 7pm for the Australian population.

“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 a first dose of AstraZeneca vaccine,” chief medical officer Professor Paul Kelly said.

“This is based on the increased risk of complications from COVID-19 with increasing age, and thus increased benefit of vaccination.

“The second recommendation is that immunisation providers should only give a first dose of AstraZeneca COVID-19 vaccine to adults under 50 years of age where benefit clearly outweighs the risk for that individual’s circumstances.

“The third recommendation is people that have had their first dose of the COVID-19 AstraZeneca without any serious adverse events can safely be given their second dose.”

Department of Health secretary Professor Brendan Murphy said the approach was taken with “an abundance of caution”, ensuring that healthcare workers under 50 in Phase 1b would be prioritised with the Pfizer vaccine.

Health Minister Greg Hunt said the government would continue to follow the medical advice as more evidence became available.

“If they advise age restrictions or other variations, we’ll do it, we’ll adopt it,” Mr Hunt said.

Outlining reasons to changes in the vaccine rollout, Mr Morrison said with Australia’s “strong position with no community transmission” that “there’s no place you’d rather be” and the government continued to act “in the best interest of Australians” on medical advice.

The moves are similar to those made in the United Kingdom, where Britain’s vaccine advisory committee advised that an alternative to Oxford-AstraZeneca’s vaccine should be given to under 30s where possible due to a “vanishingly” rare side effect of blood clots in the brain.

The implications of the decision on the vaccine rollout are yet to be widely known given it will largely affect those in the general population tipped to receive their first jab in mid-year.