Prime Minister Scott Morrison has announced the Pfizer vaccine is now the preferred option for adults younger than 50 because of blood clot concerns.

Speaking this evening, Mr Morrison said the government would exercise an "abundance of caution" based on advice from the Australian Technical Advisory Group on Immunisation and the Therapeutic Goods Administration.

The decision comes after the European Union's medical regulator announced on Wednesday it would list unusual blood clots as a "very rare" side effect of the AstraZeneca vaccine.

Wagga Glenrock Country Practice GP Ayman Shenouda, who is running the city's only mass vaccination hub, said this morning he would be guided by government advice on the vaccines.

"I think for everything we do there is a rare possibility of risks. The main important thing is to balance the risks towards the benefits of the vaccination," he said.

There have been 86 blood clotting cases out of 25 million people in Europe administered with the AstraZeneca jab.

Mr Morrison said the federal government would need to "recalibrate" its coordination of the staggered vaccine rollout, currently in overlapping phases 1a and 1b.

The AstraZeneca review is another hurdle in the federal government's rocky start to the immunisation program, which has already faced significant delays and reported supply issues.

Pfizer until now was prioritised for the most at-risk people in 1a including aged care residents and some frontline healthcare workers.

Health Department secretary Brendan Murphy said last night there would still be "a big need for AstraZeneca" to vaccinate people over the age of 50.

Associate Professor Shenouda encouraged residents to make use of the mass vaccine hub, which he said was only using about 65 per cent of its 1200 available weekly AstraZeneca jabs.

"I think what patients tell me as they book in and come and get their vaccine is that they don't know about the existence of this hub. They were surprised that this is there," he said.

People over the age of 70 and adults with underlying medical conditions or significant disabilities are among groups currently eligible under phase 1b of the rollout.

Dr Murphy said healthcare workers under the age of 50 who are eligible in this phase would now be prioritised for Pfizer, which is less readily available, meaning 1b could face delays.

Speaking this afternoon, Murrumbidgee Local Health District COVID-19 coordinator Emma Field the region's public healthcare rollout, which includes staff and aged care residents in phases 1a and 1b, had been going well and was on track for a mid-July finish.

"We have experienced quite a good uptake and quite a good amount of early adopters, so that's been quite encouraging," she said.

"The confidence from our healthcare workers is quite high. You'll always see a level of hesitancy. We have seen a little bit of that but nothing major."

However, that timeline could change because some younger MLHD staff in 1a and 1b have until now been offered AstraZeneca while others have been offered Pfizer.

NSW Health Minister Brad Hazzard, appearing on the ABC's 7.30 program on Wednesday night, called on the federal government for clearer information about vaccine supply.

"I think it's fair to say the communications probably do need to be improved a little bit with each of the states and territories," he said.

"But having said that, it is challenging for the federal government I'm sure, at the present time, to know precisely how much vaccine is coming to us from either offshore or onshore."