measles outbreaks and the role of anti-vax misinformation

Recently Grant Jacobs discussed a paper which indicates that many people strongly opposed to genetic modification think they are well-informed, but in reality know little about the subject. On current evidence, the same applies to those opposed to vaccination.

I originally sat down to write about this piece of nonsense, but it can wait. Instead – NZ readers will probably be aware of the handful of measles cases in the Waikato. It could be worse. My Twitter feed today has included a lot of updates on a rapidly spreading outbreak in the US state of Washington – an outbreak that’s seen the governor declare an emergency.

Earlier today there were 31 confirmed cases, 21 of whom were children under 10. So far, one of the 31 has been hospitalised. Most of the 31 were unvaccinated.

Those numbers are expected to rise, given that firstly: various infected, contagious people attended a football game, went to Portland’s international airport, and visited schools, hospitals, churches, and other public places. Since measles is perhaps the most contagious vaccine-preventable disease going, it’s highly unlikely that the number of cases will stop at 31. And that’s because – secondly – vaccination rates in that region are well below what’s required to ensure herd immunity. For example, Clark County (an area that includes the city of Vancouver) has a measles vaccination rate of 78%, well below the 92-94% required to maintain herd immunity. In Portland, it’s around 87%, which is still too low.

Herd immunity

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And that can be sheeted home to what the WHO has described as ‘vaccine hesitancy’, driven to a large degree by those who are opposed to childhood vaccinations. They push the line that diseases like measles are ‘benign childhood diseases’, which is a pretty awful attitude when you consider that 1-2 of every 1000 children with measles will die of complications, and that a number will be hospitalised. We’ve seen this play out already in the ongoing outbreak in Europe, and remember that at the global level an estimated 110,000 children died of measles in 2017.

And consider this: those infected with measles are also at risk of subacute sclerosing panencephalitis (SSPE) – a chronic & progressive inflammation of the brain caused by the measles virus. There’s no cure; it’s usually fatal. The odds are ~ 1 in 10,000 – but may be as low as 1 in 609 for those infected as babies.

The risk of harm from the disease itself is considerably higher than the risk of serious side-effects from the vaccination. In addition, developing measles lowers the immune response to other pathogens for at least 2 years post-infection. And that’s not counting the social and economic costs of the illness.

Nor is there any evidence for the claim, first made in 1998 by discredited UK doctor Andrew Wakefield and pushed ever since by those opposed to vaccination, that the MMR vaccine causes autism. In contrast, there is evidence that there’s a strong genetic component to autism. Nonetheless, and in line with the paper Grant discussed, research published last year (Motta, Callaghan & Sylvester, 2018), and also discussed in The Spinoff, found that

More than a third of respondents in [the] sample thought that they knew as much or more than doctors (36%) and scientists (34%) about the causes of autism. [The] analysis indicates that this overconfidence is highest among those with low levels of knowledge about the causes of autism and those with high levels of misinformation endorsement. Further, [the] results suggest that this overconfidence is associated with opposition to mandatory vaccination policy. Overconfidence is also associated with increased support for the role that non-experts (e.g., celebrities) play in the policymaking process.

Sadly, none of that stops vaccine opponents pushing their wrong-headed message: it’s been estimated that 50% of all parents with young children have found misinformation about vaccines via social media**. (I strongly suggest reading this take on the various – and complex – motives underlying its spread.)

And we’re now seeing the results play out in Washington in real time, just as we have in Europe & may well see here in NZ if herd immunity drops as a result of that misinformation. A very sad state of affairs.


** You can access the full report here; it’s well-written & accessible.

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