Tasmania's health department is cancelling first-dose Astra Zeneca vaccination appointments for people aged under 50.
It's in response to advice that the Pfizer inoculation is now the preferred vaccination for people aged under 50, due to Astra Zeneca's very rare side effect of blood clots.
People of any age who've already received a first dose of Astra Zeneca with no ill effects are considered safe for their second.
Tasmanians with existing first-dose appointments at community clinics will be contacted directly to discuss rescheduling their appointments.
Those who have had their first dose will also be contacted directly by the Public Health Hotline.
Infectious Diseases Physician doctor Paul Griffin has told Nine the move is an abundance of caution, and any risk is extremely rare.
"We're talking a few cases per million doses, and the majority of those people will survive and recover from this, so it is something that is exceedingly rare," he said.
"It shouldn't undermine our confidence overall."