Thousands of Aussies not fully immunised

Almost half a million young Australians - aged between 10 and 19 - are not fully immunised.

It comes as the federal government expands a program to provide free catch-up vaccines to those aged 19 or under and all refugees and humanitarian entrants.

"The expansion of the program will allow these groups to access free catch-up vaccines equivalent to those received in early childhood," Health Minister Greg Hunt said in a statement on Saturday.