Anatomy of a health scare: Education, income and the MMR controversy in the UK
Introduction
Immunization is a proven tool for controlling and even eradicating disease, sparing people from suffering, disability, and death. The World Health Organization estimates that immunizations avert about three million deaths every year. The importance of trust in vaccines can hence hardly be overstated. In this paper we consider a recent episode when trust in one particular vaccine, the combined measles, mumps, and rubella (MMR) vaccine, was eroded in the UK due to a number of claims by some researchers, starting in early 1998, linking the vaccine to the development of autism in children. The MMR controversy provides an interesting case where, for a short period of time, research publicized in the media, suggested a potential risk of serious side-effects associated with a standard medical procedure, where there was also a sharp behavioral response from the public. We consider the controversy from the perspective of health inequalities and the diffusion and assimilation of information on advances in medical knowledge, focusing on whether and how vaccine uptake behavior in the wake of the controversy differed among groups of parents with different levels of education and income.
In February 1998 the British medical journal The Lancet published a report on twelve children with developmental disorders. While the paper did not claim to prove any link between the syndromes and the MMR vaccine, some of the surveyed parents blamed the combined vaccine, saying that the symptoms had set in days after receiving the immunization. Dr Andrew Wakefield, who led the research, suggested that there was a case for administering the three vaccines separately until further research could rule out the combined vaccine as an environmental trigger. Between 1998 and 2002, the claim of a potential link between the particular combined vaccine and autism was reiterated on a number of occasions by Wakefield and increasingly in the UK media. Confidence in the MMR vaccine declined as did uptake, with the latter dropping by over ten percentage points in five years. However, by 2003, a substantial body of research had failed to verify any link between MMR and autism, and a consensus among researchers emerged that the vaccine was safe to use.1 Vaccination levels began to rise again, but not to the level seen before the controversy.
There is mounting evidence suggesting that education and income have causal effects on health outcomes. One of the hypotheses to receive recent attention in the economics literature is that more educated individuals have better understanding of, and more quickly absorb, information on advances in medicine. The MMR controversy provides a useful case for studying individual behavioral responses to new information for several reasons. First, the controversy took place over a relatively short period and the response is known to have been strong. Moreover, the fact that the initial information was subsequently overturned and the decline in uptake reversed gives us confidence that our results are not driven by other unrelated trends. Second, childhood vaccines are provided free of charge through the National Health Service (NHS): parents can either accept or reject them at no monetary cost.2 Rejecting a given vaccine leaves the child unprotected against the disease while a decision to accept it carries with it a risk of potential side effects for the child.3 Hence the parents decision problem can be characterized as a binary choice where neither option has any direct cost and where the objective is to choose the option with the least risk for the child’s health. Finally, the risk information coming from different sources regarding the safety of the MMR vaccine was, at times, contradictory. Experimental evidence (Viscusi, 1997) suggests that individuals making decisions under such uncertainty give undue weight to information indicating a high risk, while information indicating low risk, especially when provided by the government, is under-weighted.
For our main analysis we use data on the variation in the uptake of the MMR, and other childhood immunizations, across local Health Authority areas for the years 1997–2005, which we combine with corresponding data on education, incomes and other characteristics of the local populations obtained from the Health Survey for England (HSE). We find that the uptake rate of the MMR declined faster in areas where a larger fraction of parents had stayed in education past the age of 18 than in areas with less educated parents. Projections from these estimates suggests that the uptake rate by high educated parents fell by around 10 percentage points relative to the uptake rate by parents with low education over the period 1998–2003, leading to a negative education gradient in uptake at the peak of the controversy. Most of the relative decline in uptake also appears to have occurred during the early stages of the controversy when media attention was now widespread and the uncertainty surrounding the efficacy of the vaccine high. We also find, however, that the uptake of other uncontroversial childhood immunizations declined in relative terms in areas with more educated adults, suggesting a “spillover” effect from the MMR controversy.
After analyzing the area level data, we consider data from the Millennium Cohort Survey (MCS) which follows a set of children born in the UK within a twelve month period starting in September 2000. These children were due the MMR vaccine at the height of the controversy and the survey therefore provides an excellent opportunity for studying in more detail the behavior of parents at that point in time using micro-level data. Analysis of this data allows us to confirm that there was, at the peak of the controversy, negative education and income gradients in the uptake of the MMR even after controlling for a large range of potentially confounding individual characteristics. Indeed, of all the vaccines freely provided through the NHS, the MMR is the only vaccine for which we observe a significant negative effect of income on uptake. For this vaccine parents had the option of purchasing alternatives, in the form of single vaccines, in the private market, and the MCS allows us to measure this.
The outline of the paper is as follows. Section 2 provides a background, including a research and media timeline. Section 3 describes the area-level data and the trends in the uptake of childhood immunizations. Section 4 presents the results from the analysis of this data while Section 5 provides further evidence based on the cohort survey data. Finally, Section 6 provides a discussion.
Section snippets
Literature review
A positive relationship between education and health is found in most of the literature (see Grossman, 2006, Cutler et al., 2008 for extensive reviews) as more educated individuals are more efficient producers of health (Grossman, 1972) or make better choices of input mixes (Rosenzweig and Schultz, 1982), possibly due to differences in access and use of health information.4
The data
We first use area-level data for England. The geographic areas that will serve as our unit of observation are the 95 Health Authorities (HA) introduced in April 1996.14
The model and results
The main hypothesis that we wish to test is whether the change in an area’s uptake rate, during the controversy, is correlated with fraction of its population that has a high level of education. One option available to parents rejecting the MMR would be to purchase single vaccines (see below). However, single vaccines would come at a substantial cost to the parents, which would suggest a potentially important role played also by household income.
In order to consider the role of education and
Further evidence
In this section we supplement our earlier results with further evidence using data from the MCS. The MCS follows the lives of a set of children born in England between September 2000 and August 2001. Recalling that children in the UK are due the MMR at around the age of 13 months this implies that, in terms of Fig. 1, the first MCS children would have been due the MMR between the final quarter of 2001 and the third quarter of 2002 (marked in dark gray). Hence the MCS cohort were due the
Discussion
In this paper we have considered a recent episode when trust in a particular vaccine, the combined measles, mumps, and rubella (MMR) vaccine, was eroded due to a number of claims by some researchers, starting in early 1998, linking the vaccine to the development of autism in children. Over the following five years, the claims of a link were met with counterclaims and with government reassurances about the safety of the vaccine. By 2003 the claims had been resoundingly rejected by subsequent
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