PUBLIC health advocates have long been frustrated at how hard it is to persuade vaccine-hesitant parents of the safety and benefits of immunisation.
One study published last year found educational interventions with parents could actually make them less likely to vaccinate their children.
The randomised controlled trial looked at four interventions: explaining the lack of scientific evidence for a causal link between the measles–mumps–rubella vaccine and autism; providing written information on the dangers of the diseases prevented by that vaccine; showing images of children affected by the diseases; and telling the dramatic story of a child who almost died from measles.
None of those four strategies increased parents’ intention to vaccinate, and the last two actually increased parental belief in the dangerous side-effects, not of the diseases, but of the vaccines that prevent them.
So why are anti-vaccine messages so persuasive and so resistant to scientific evidence?
A study of nearly 500 anti-vaccination websites presented at last week’s American Public Health Association annual meeting set out to examine those questions.
Around two-thirds of the sites linked vaccines to autism, and about 40% raised concerns about brain damage or injury. Just over a quarter argued vaccines were ineffective and a similar proportion argued they weakened the child’s immune system.
Techniques used to promote the anti-vaccine views included “expert” opinion, pseudo-scientific evidence (like this example), anecdotes about alleged vaccine-related injury, and the fostering of mistrust in relation to those recommending vaccination.
Government was the most common target of mistrust (79% of sites), followed by health care professionals (42%). Reasons for mistrust included the belief that authorities lacked concern for people’s wellbeing (82%), were ignorant of vaccine dangers (78%), or were motivated only by profit or power (70%).
One site, allegedly written by a medical professional, says: “Vaccines are immoral when they are forced upon an innocent and ignorant public by an insane system of ‘public health’ and pediatricians who are often in total denial of the negative effects of their own actions”.
Widespread claims that government and health care practitioners were liars, ill informed or engaged in a conspiracy were particularly disturbing, the researchers argued, given these are the people and organisations we rely on to deliver quality messages on immunisation.
If those sources aren’t trusted, there is little chance their messages are going to get through.
One solution, the researchers suggest, might be to associate the pro-vaccination message with other beliefs held by vaccine-hesitant parents. Many of the anti-vaccine sites also promoted healthy behaviours such as good nutrition and breastfeeding, for example, a possible common ground for public health advocates.
It might also be possible to get the message out through organisations or people these parents do trust — parents’ groups, perhaps, or health food stores.
Perhaps, most crucially, many of the sites use ideas about freedom and individual choice to bolster their arguments, prompting these researchers to suggest immunisation advocates should be careful not to use language that implied any restriction of individual freedom — which might raise questions about the federal government's “no jab, no pay” policy.
The researchers argue that there might even be a way to convince parents that vaccination, far from impinging on their child’s freedom, actually enhances it.
Jane McCredie is a Sydney-based science and medicine writer.