Parents in the United States who are hesitant about vaccinating their children are strongly concerned with the moral values of purity and liberty, reports a paper published online this week in Nature Human Behaviour. The study suggests that information campaigns that incorporate these values, rather than focusing on ideas of fairness or preventing harm, may be more effective.

Despite information campaigns highlighting the individual and collective dangers of under-vaccination, reluctance to vaccinate children is a persistent issue among parents in the US.

Avnika Amin and colleagues conducted online surveys of 1,100 US parents of children aged under 13. The questions assessed the participants’ level of child vaccination hesitancy and explored how important different moral values were to them when deciding if something was right or wrong. The authors find that highly vaccine-hesitant parents are twice as likely to emphasize liberty and purity moral values compared with low-hesitancy parents (where liberty is associated with belief in personal responsibility, freedom, property rights and resistance to state involvement in citizens’ lives, and concerns about purity centre around boundaries and protection from contamination). They also show medium-hesitancy parents are twice as likely as low-hesitancy parents to emphasize purity.

The authors note that few studies have looked at the potentially powerful issue of moral values in relation to anti-vaccination sentiments. Although the results of their work are correlational - and therefore a causal link cannot be drawn - they suggest that investigating the moral foundations of people’s health decisions could be a fruitful area for improving public health communications.