The controversy over MMR that Andrew Wakefield managed to trigger in the U.K. with his botched Lancet study, has given researchers the opportunity to study the dynamics of a public health scare. Their report, "Anatomy of a Health Scare: Education, Income and the MMR Controversy in the UK" studies the relationship between the media, certain family attributes, and uptake of the MMR vaccine [1]. Their findings call into question conventional wisdom regarding the positive role of parent education in vaccine uptake.

Most people will know the basic history of the MMR controversy, so I won't cover it here. If you want a refresher, Wikipedia has a convenient overview. This paper isn't about the vaccine itself, but of the dynamics of the scare. "The case of the MMR controversy provides an interesting case where, for a relatively short period of time, some research, publicized in the media, suggested a potential risk of serious side-effects associated with a standard medical procedure and where there was a sharp behavioral response."

The first question to ask, is how much do parents rely on the media for information about vaccines? The authors cite two previous studies, one American, one British, both released in 2000. The American study [2] asked the general question "Where do you get information about immunizations?" 84.2% answered "doctor", while 18.1% referred to newspapers and magazines, and 12% to books or journals. In contrast, British version [3] asked specifically where parents obtained information about the potential side-effects of MMR. Now the most popular answer wasn't their doctor, but the television (35%). Clearly then, the media had a big role to play in driving the MMR controversy.

The authors were interested in a large body of research by economists, that looks at the relationship between a person's education and their health outcomes in life. A general hypothesis being floated around the economics community at the moment is that the more educated somebody is, the better equipped they are to understand and absorb new information about health. To see if this was true, the researchers looked at vaccine uptake behaviour among groups of parents with different levels of education and income, and compared this with statistics on MMR coverage in the media, using the BBC as a representative example. A further dataset they used was the results of surveys of parental attitudes to immunization tracked across the period. All this data covered the period 1998 - 2005.

Their results are interesting, and counterintuitive. They suggest that during the controversy, education was negatively correlated with vaccine uptake. In other words, the more educated parents responded far more strongly to the MMR hysteria than the less educated. Not only that, but the decline in MMR uptake spilled over to other vaccines, in the same demographics. Income also played a part, but much a smaller one - parents with higher incomes were more likely to switch to single vaccine alternatives.

The effect of income is somewhat understandable - the MMR vaccine is free, while single shot alternatives cost money which lower income families can ill afford. The finding that more educated parents were more inclined to panic in the face of the controversy though is completely out of the blue, and at odds with what the authors describe as the "routine observation in the literature that parents with high levels of education have the highest uptake rates of childhood immunizations."

In order to double check it, the authors controlled every conceivable variable - much of the mammoth 58 page paper is taken up with this statistical exercise covering (among others) ethnicity, mother's age, smoking, language, marital status, internet access, quality of he neighbourhood, religion, political leaning and geographical region - but still the negative relationship between education and vaccine uptake remains.

Why?

It seems to come back to the hypothesis from economics, that "more educated individuals more quickly absorb new health-related information". Absorb they did, regardless of whether the information was correct or not. Worse, the "spillover" of the effect into other, non-controversial vaccines demonstrates that many of these parents fell victim to an irrational, "alarmist" reaction. Educated people it seems expose themselves to more information, but they aren't necessarily any better at evaluating it.

The authors note that this fits in neatly with research from the behavioural-theoretical literature, citing an paper by Viscusi [4], who argued that people give undue weight to high-risk information, and that low-risk information - especially that provided by the government - is underweighted. With irresponsible sections of the British press joining with pressure groups such as JABS to promote the scare, the resulting drop in vaccine uptake is unsurprising, and was most pronounced in those people with the greatest exposure to the hype.

I'll finish with a quote from the authors that I think neatly sums up why this kind of research is important. "Immunization is a proven tool for controlling and even eradicating disease, sparing people from suffering, disability and death. The World Health Organization estimate that in 2002 immunization averted about two million deaths. The importance of trust in vaccines can hence hardly be overstated.

[1] Anderberg, D., Chevalier, A., Wadsworth, J. (2008). Anatomy of a Health Scare: Education, Income and the MMR Controversy in the UK. IZA Discussion Paper Series, n/a(3590), 1-58.

[2] Gellin, C., Maibach, E.W., Marcuse, E.K. (2000). Do Parents Understand Immunization? A National Telephone Survey. Pediatrics, 106, 1097-1102.

[3] Pareek, M., Pattison, H. (2000). The Two-Dose Measles, Mumps and Rubella (MMR) Immunization Schedule: Factors Affecting Maternal Intention to Vaccinate
. British Journal of General Practice, 50, 969-971.

[4] Viscusi, K., , . (19977). Alarmist Decisions with Divergent Risk Information. Economic Journal, 107, 1657-1670.

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