3 Risk perception
At first glance, the public response to the risk of a link between MMR and autism appears to be wildly disproportionate. From a scientific point of view, an association is unsupported by major epidemiological studies involving vast numbers of participants. Neither has evidence been presented of a plausible biological mechanism. Common sense would seem to dictate that the claim to any link simply lacks credibility and well-informed parents should behave ‘rationally’ and allow their children to be immunised, or else run the very real risk of exposing children to potentially serious diseases (see Table 1).
Table 1 Symptoms of measles, mumps and rubella (after Fitzpatrick, 2004, p. 2).
|Measles||Fever, rash, cough, sore eyes, swollen glands, loss of appetite||Ear infection, pneumonia/bronchitis, convulsion, diarrhoea, meningitis, death|
|Mumps||Swollen glands, fever, headache, abdominal pain, loss of appetite||Swollen testicles, meningitis/encephalitis, pancreatitis, deafness, miscarriage|
|Rubella||Fever, headache, rash, sore eyes, cough, swollen glands, joint pains, loss of appetite||Encephalitis, bleeding disorders. In pregnancy: deafness, blindness, heart problems, brain damage in foetus|
These symptoms and complications are unpleasant at best and life-threatening at worst. Yet it may be worth considering the extent to which today's parents have witnessed the diseases of measles, mumps or rubella. A study by Gore et al. (1999) into the factors that affected parents' decisions to immunise found that in communities where infectious diseases were rarely witnessed, immunisations were often considered to be redundant.
Click to view, Bellaby, P. (2003) ‘Communication and miscommunication of risk: understanding UK parents' attitudes to combined MMR vaccination’, BMJ, 327, pp. 725–28. Bellaby argues that parents' responses to the MMR controversy are not necessarily irrational. What factors does he use to support his argument?
One of Bellaby's points is that ‘the case evokes cultural and social context rather than “economic man”’ (‘economic man’ is an economist-theory model of human behaviour, which presumes that people act entirely in their own self interest). He shows that context often proves decisive in decision making by parents about whether to allow their children to be immunised with the MMR vaccine.
Although risk is always a social evaluation, rather than a natural phenomenon that can be separated from its context, risk experts often refer to the qualitative aspects as ‘the social amplification of risk’. A combination of circumstances makes certain events seem more risky than the orthodox scientific assessment would have it. One of the main driving forces is the perception of ‘fright factors’. These are characteristics of a controversy that elevate levels of alarm. Bennett (1999) has summarised these ‘fright factors’. He argues that risks are generally more anxiety-inducing if they are perceived to:
be involuntary rather than voluntary
be inequitably distributed (some benefit while others are adversely affected)
be inescapable by taking personal precautions
arise from an unfamiliar or novel source
result from artificial rather than natural sources
cause hidden and irreversible damage
pose particular danger to small children or pregnant women, or to future generations
threaten a form of death or illness arousing particular dread
damage identifiable rather than anonymous victims
be poorly understood by science
be subject to contradictory statements from responsible sources.
Go through this list of ‘fright factors’ and note down which of them apply to MMR and why.
It quickly becomes apparent that the MMR vaccine controversy rates very highly indeed on ‘fright factors’ compared with other types of risks that might, statistically, be more likely to occur. A scientific assessment of risk, which focuses on mathematical probabilities, often tends to ignore these ‘fright factors’, whereas public perceptions tend to prioritise them over statistical and experimental data.
Indeed, assessments of risk are rarely objective. Value judgements, impossible to measure scientifically, often frame individuals' reactions to risk. Thinking of your own response to risk, you might prioritise or downplay certain ‘fright factors’ in any one situation depending on your moral, political, ethical or religious stance.
Scientists have a tendency to frame risk in terms of effects on populations whereas lay people (non-experts, so to speak) tend to be concerned with individuals. This is particularly relevant to an issue such as immunisation where we can see immediately that there may be a tension between a scientific and a lay perspective. No vaccination is without some degree of risk to the individual, however small. Yet for a mass immunisation policy to work, a significant proportion of the population needs to be immunised to achieve ‘herd immunity’ (estimated to be 95% for MMR by the World Health Organization). Scientifically (and politically) the small risk of an adverse reaction is seen as a price worth paying. Most governments acknowledge the inherent unfairness of this. In Britain, in the event of a serious reaction, parents can apply for vaccine damage payments to compensate for ‘sacrificing’ their child's health for the public good. However, financial compensation is likely to be of little comfort to parents whose children have been disabled through vaccine damage.
As the collective memory of diseases like measles and mumps recedes, the risk of adverse effects comes into sharper focus. An appeal to social responsibility in maintaining herd immunity may matter less to parents who perceive the risk of autism to be greater than the risk of contracting measles or mumps. The benefits of protection conferred by immunisation and the risk taken of adverse effects is an individual one, but the risks of transmitting an infectious disease when herd immunity is not maintained are social as they extend to those beyond the MMR dissenters. Indeed, the groups most vulnerable to mumps, measles or rubella are babies too young to be immunised and teenagers whose vaccinations predated MMR, many of whom were not immunised for mumps.
Fitzpatrick (2004) provocatively speculates that for some parents the decision to refuse the MMR triple vaccine has little to do with medical science per se.
Middle class discontents became apparent around a range of political issues: fuel prices, student loans, blood sports and the invasion of Iraq. Yet MMR provided a focus for protest that was both intensely personal and highly political … The controversy over immunisation allowed scope for individual initiative, at least in the form of a gesture of defiance, which was generally lacking in the public sphere.
(Fitzpatrick, 2004, p. 56)
While, for some, withholding immunisation may have had an element of political defiance, for others it was the path of least resistance. Taking a child to be vaccinated is a distressing experience at the best of times. For parents uncertain about what to do, the balance easily tips in favour of postponing a decision or doing nothing (Scottish Executive, 2002).
The picture painted here is that the scientific consensus on the risk that the MMR triple vaccine causes autism is hugely disproportionate to the public perception of that risk – a perception that is influenced by a much wider range of factors. Parents might appreciate that mainstream scientific consensus is that the MMR triple vaccine poses a negligible risk, but these ‘informed dissenters’ may still decide not to immunise their children for a variety of personal or political reasons that have little to do with science.