A doctor can talk a hesitant parent into vaccinating their child, according to a new study, but it may not be the kind of talk you'd assume.

Forget sweet-talk or collaboration. Instead, doctors who simply presume that parents are going to vaccinate have greater success.

Researchers out of the University of Washington, the University of California and Portland State University looked at data from 111 vaccine discussions involving 16 providers from nine practices. Half of the parents involved were labelled "vaccine-hesitant parents" using a questionnaire.

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What happened next depended on the "initiation format" used by the doctor. That is, his or her opening line.

They found that most providers (74 per cent) started with "presumptive" language such as, "Well, we have to do some shots," rather than "participatory" phrasing such as, "What do you want to do about shots?"

"Parents had significantly higher odds of resisting vaccine recommendations if the provider used a participatory rather than a presumptive initiation format," writes lead author Douglas Opel of the department of pediatrics at the University of Washington.

When parents resisted, 50 per cent of providers pursued their original recommendations - saying, for instance, "He really needs his shots," and 47 per cent of those resistant parents then agreed.

The study, appearing online Monday in the journal Pediatrics, is part of a burgeoning research field scrambling to figure out how vaccine-hesitant parents (VHPs in the literature) arrive at their skepticism and what medical professionals can do to convince them to immunize their children. It comes on the heels of other research out of Texas State University finding that a person's social networks can heavily influence a parent's decision whether to vaccinate.

This is of particular concern to Opel, who writes that the proportion of parents who have concerns about vaccines remains high and that rates for non-medical exemptions for required school-entry vaccines are increasing annually. In Canada, similar trends are at play. Recent measles cases in British Columbia and Alberta have raised further alarm bells.

Opel suggests more research is needed to flesh out the link between a medical practitioner's style and his or her success with vaccinating patients.

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The most recent findings, he says, challenge expectations that parents and practitioners may have about the best way to communicate about vaccines.

Using a collaborative approach, "may need to be reconsidered if it leads to fewer children being vaccinated and/or vaccinated on time," he writes.