Vaccine hesitancy: what 25 years of social science actually shows

Hesitancy isn’t a personality trait, and it isn’t a lack of information. After 25 years of behavioural and social research, including the substantial Australian contribution from NCIRS through the SKAI program, the picture is clear: hesitancy is a context-dependent, multi-causal phenomenon shaped by trust, perceived risk, social networks, identity, and clinician communication. The good news, it’s also responsive to specific, evidence-based interventions.

Hesitancy is a spectrum, not a category

The WHO Strategic Advisory Group on Immunisation defined vaccine hesitancy in 2014 as “a delay in acceptance or refusal of vaccines despite availability of vaccine services.” The key word is delay. Most hesitant people do vaccinate, eventually, sometimes, partially, or for some vaccines but not others. Confident acceptors and hard refusers sit at the extremes. The much larger middle is “cautious acceptors” who have specific questions, time-sensitive concerns, or are waiting for the right moment.

The 3Cs and 5As frameworks

3Cs (WHO SAGE)

• Confidence. Trust in the safety and effectiveness of vaccines, the system delivering them, and the policy makers behind them.
• Complacency. Perceived low risk of disease. When measles hasn’t been seen locally for a decade, motivation to vaccinate against it drops.
• Convenience. How easy is it physically and economically? Clinic hours, geography, cost, language access.

5As (extended model)

• Access. Service availability.
• Affordability. Out-of-pocket cost.
• Awareness. Knowing what to vaccinate, when, where.
• Acceptance. The classic 3C territory.
• Activation. What actually moves a person from intending to vaccinate to vaccinating? Reminders, opportunistic offers at the GP visit, defaults.

Why classic “information” campaigns underperform

Research consistently shows that one-way information campaigns aimed at correcting misinformation produce small, sometimes negative effects. Two main reasons.

First, backfire and reactance. Direct refutation of strongly held views can entrench them, particularly when the rebuttal carries authority cues that the listener doesn’t trust.

Second, identity protection. Vaccine views often correlate with broader identity, parenting style, political affiliation, trust in institutions. Information that contradicts identity is harder to update than information that doesn’t.

What does work, the SKAI evidence base

Australia’s SKAI program, developed and curated by NCIRS, distilled the social-research evidence into a clinician-facing framework. Core principles:

• Listen first. Ask, “What questions do you have about this vaccine?” before assuming the concern.
• Personalise the risk-benefit calculation. “For your child, at this age, here is what we know.”
• Affirm the underlying motivation. Most hesitant parents are motivated by deep care for their child, the conversation works better if it starts there.
• Share clinical experience. Vaccinated outcomes you’ve seen, not statistics. The brain processes story differently to data.
• Make a clear, presumptive recommendation. “Your child is due for the 18-month MMR today, are you ready to go ahead?” outperforms “What would you like to do?”
• Leave the door open. A “no” today is not forever. Most repeat-decliners eventually move some part of the schedule.

Motivational interviewing

Motivational interviewing (MI) is a structured conversational style originally developed for addiction medicine. Applied to vaccination, MI uses open-ended questions, reflective listening, affirmations, and exploration of ambivalence rather than persuasion. Australian and Canadian trials in well-baby clinics have shown that brief MI conversations at 2-month visits measurably improve vaccination by 24 months. The technique is teachable; most workshops take a day.

Structural factors matter more than people think

For all the attention on conversation skills, the biggest gains usually come from structural changes: extended clinic hours, defaults that opt people into vaccination, reminder/recall systems, removing co-payments, embedding vaccinators in places people already are (workplaces, schools, pharmacies). Australia’s school-based program achieves coverage levels that no amount of communication would produce in a stand-alone clinic.

What this means in practice

For clinicians: lead with the question, listen, affirm, share clinical experience, make the recommendation, and don’t moralise. For parents: it’s legitimate to have specific questions, and the best place to raise them is with a clinician you trust, ideally in person rather than online. For policy: the largest population-level gains come from making vaccination the easy default at the points where people already are.