A university says children from poorer families are less likely to be fully immunised, but not because of parents' anti-vaccination attitudes.

Anti-vaccination beliefs aren't the main reason almost 10 per cent of Australian children remain unimmunised.

Family finances, access to services and chronic health conditions are key factors in why some parents don't keep their children's injections up to date, a University of Adelaide study has found.

Children living in a large household or those of single parents were also at risk of not being properly protected.

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Out of 9.3 per cent of unimmunised children, only one-in-six had parents who disagreed with vaccinations.

"Socio-economic disadvantage was an important reason why parents had children who were either partially-immunised or not immunised at all," associate professor Helen Marshall said.

"Children with chronic medical conditions were also more likely not to be up-to-date with immunisations."

The study, published in the journal Vaccine, looked at 5000 children aged between three and 19 months.

Prof Marshall said the findings could help programs designed to increase the uptake of vaccinations.

"Reminders and rescheduling of cancelled appointments and offering immunisation in different settings may help achieve better protection for children and the community," she said.