Prime Minister Scott Morrison announced the Pfizer vaccine is the preferred option for adults younger than 50 - following blood clot concerns associated with the AstraZeneca vaccine.

The European Union's medical regular listed unusual blood clots as a "very rare" side effect of the AstraZeneca vaccine on Wednesday.

Since the vaccine rollout began last month, hospitals and general practices in the MIA have only been provided with AstraZeneca doses.

Your Health Griffith operator Keith Fletcher, who is running the city's mass vaccination hub, said only a very small percentage of people currently eligible for the vaccine are under 50 and the rollout will mostly continue as planned.

"With the current guidelines, the only people under the age of 50 who can receive the vaccine are health care workers and people at high risk, they might have to wait a little bit longer but for every one else it stays the same," Mr Fletcher said.

"Any changes will be very minor."

Mr Fletcher said the Griffith Vaccination Hub would follow advice from the Australian Technical Advisory Group on Immunisation and the Australian Government as it is released.

Earlier this week, MIA general practices suggested concerns over blood clots may have caused a drop in the number of residents receiving the jab.

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

Speaking this week, Murrumbidgee Local Health District COVID-19 coordinator Emma Field said 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.

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