Public goods and bads – vaccinations and measles (and mumps and rubella)

There has been a disturbing trend in the past decade for parents in the UK to refuse vaccinating their young children with the Measles Mumps and Rubella (MMR) vaccine. This has been due to the (now debunked[1, 2]) scare following a paper in The Lancet by Andrew Wakefield that claimed that MMR Jabs could be responsible for increasing the likelihood of children developing autism.

Unfortunately, despite the findings that Wakefield and his team had manipulated data, the striking off of Wakefield from the medical register and the full retraction of The Lancet paper, some parents continue to refuse vaccinating their children. The refusal of parents to vaccinate their kids is not the end result of this story, and their (unfortunate) children were not the only victims.

This is because the MMR Vaccine is not 100% effective [3] and is not given to everyone, namely, not to vulnerable parts of the population, including babies less than 1 year old and children who have a compromised immune system (for example those with AIDS or receiving chemotherapy). Normally, with high rates of vaccinations, these issues would not be a problem, as the ‘herd immunity’ would provide them with protection – the more people immune to infection, the less chance there is for someone without immunisation to come in contact with the infection. But as MMR vaccinations fell below the measles herd immunity threshold (94% [4, 5]) outbreaks of measles started occurring, affecting those children whose parents chose not to vaccinate them, but also those whose vaccinations had not been effective and the vulnerable population. In 2008, measles was declared to be endemic again in the UK after a break of 14 years [6] and a measles outbreak was recently declared in Merseyside [7]. Additionally, a recent story in the US paper USA Today reported that travellers from the US to, among other destinations, Western Europe were bringing back measles and infecting unvaccinated populations in the US [8].

Vaccinations are one of the most cited examples of ‘positive externalities’ – an idea in economics that in some circumstances society experiences benefits greater than the benefits received by individuals making the decision. There are also negative externalities – where society experiences costs greater than the costs incurred by individuals making the decision.

The MMR vaccination can be seen as both a positive and a negative externality – those who have received the jab decrease the possibility of outbreaks and therefore the possibility of you or I contracting measles (or mumps or rubella). This is a benefit for us that probably wasn’t taken into account by those who received their vaccination, so it is a positive externality. But we can also look at the lack of vaccination as a negative externality – as MMR jabs have become the norm, those who haven’t been vaccinated increase the chance of outbreaks and affect those who were unable to receive the vaccination or for whom the vaccination wasn’t effective.  This is an unintended and unaccounted consequence of the decision of parents to refuse vaccination for their children.

Another economic idea that is relevant here is that of the ‘public good’ – a good that is non-rival and non-excludable. This means that someone can consume the good without reducing the ability of anybody else to consume the good, and that it is not possible to exclude anyone from consuming the good. Herd immunization (and individual immunizations to a lesser extent) can be seen as a public good – everybody benefits from higher immunization rates and my enjoyment of the benefit doesn’t decrease your enjoyment of the benefit.

These ideas of externalities and public goods are highly relevant to environmental economics and are used on a daily basis in our work. Clean air and water and a stable climate are examples of public goods while pollution and carbon emissions are negative externalities that affect these public goods (public bads if you like). Environmental economists try to help decision makers take externalities into account through identifying and valuing externalities and contributing to design policies that make these externalities be explicitly taken into account in prices and behaviours (what we call ‘internalised’), such as a carbon or pollution tax or market-based instruments such as the sulphur and carbon cap and trade markets.

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[1] The Lancet – Retraction – Ileal-lymphoid-nodular hyperplasia, non-specific colitis, and pervasive developmental disorder in children

[2] Wikipedia – MMR Vaccine controversy

[3] Bupa – Measles, Mumps and Rubella (MMR) Vaccine

[4] Wikipedia – Herd immunity

[5] BBC News – Measles outbreak ‘worst in years’

[6] Health Protection Report – Confirmed Measles cases in England and Wales – an update

[7] Merseyside measles outbreak declared

[8] USA Today – Unvaccinated behind largest U.S. measles outbreak in years

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