Tuesday, 9 October 2012

Immunisation uptake, younger siblings and autism

There is one topic which has created more [heated] discussion and column inches in various contemporary (and indeed historical) autism circles than perhaps any other: the issue of immunisation and whether or not vaccine administration is linked to the aetiology of some cases of autism. Just reading that opening sentence may have either gained or lost this blog post viewers depending on what perceptions and viewpoints are held on the matter.

On that basis I admit to be more than a little nervous about posting about the study by Ghassan Abu Kuwaik and colleagues* on immunisation uptake in younger siblings of children with autism for fear that (a) mere mention of autism and vaccines might reignite smouldering arguments and (b) a worry that saying the wrong word here or there in this post may offend someone somewhere and detract from the science being discussed. Indeed I often feel it is quite an unfortunate situation that has been reached in this whole affair when such worries as these carry over to the discussion of science. I will therefore apologise now to anyone who takes offence at anything discussed in this post and ask that any reader comments on this post be confined to the paper itself.

So briefly the abstract:

  • Abu Kuwaik and colleagues undertook an analysis of immunisation (UK spelling) status in younger siblings (n=98) of children with autism (n=98) compared with controls (n=65). 
  • One or more immunisations were delayed (48%) or declined (12%) in a sizable proportion of siblings (25% of whom had also received an autism spectrum disorder diagnosis, ASD).
  • Of the children with autism themselves, 16% had a delay in one or more immunisation and in one case declined.
  • Nine percent of controls had one or more immunisation delayed (none declined).
  • To quote: "The rates of autism spectrum disorder diagnosis did not differ between immunized and nonimmunized younger sib[ling] groups, although small sample size limits interpretability of this result".

I find this to be an interesting paper from quite a few perspectives. Given the nature of the research, I assume the authors must have already been aware of a trend towards differences in vaccination rates among some children with a sibling with autism just as there seems to be in relation to children with autism themselves**.

I interpret this to mean one of a few possible things based on the decision to delay or withhold vaccination by some parents of children with autism stemming from (i) personal observations of a perceived 'reaction' to vaccination in their child with autism, or (ii) some effect derived from either media or discussions with others who have similarly noted a reaction to vaccination in their child with autism or (iii) a reduced perception of the importance of immunisation (as per this article***). Further, the same logic must imply that there is either a view of some degree of familial 'susceptibility' to such a response to immunisation or that the perceived risk of immunisation being linked to the appearance of autism in first offspring although perhaps 'one-off' is strong enough to warrant a modification of views on the value of immunisation for later children. By saying all that I hope I'm not trying to over-analyse the situation.

The authors conclude that: "Parents who already have one child with autism spectrum disorder may delay or decline immunization for their younger children, potentially placing them at increased risk of preventable infectious diseases". I find this also to be an interesting statement in terms of how the cost-benefit ratio works. I don't believe many people would, with hand on heart, deny the population health benefits of mass immunisation alongside other advances in medicine and hygiene, just in the same way that most people would accept that immunisation is a medicine, and medicines do unfortunately have side-effects for a few. The point is that the perceived risk of infections like measles, pertussis, meningitis or chicken pox (varicella) must have been weighed up and estimated as comparatively low**** (bearing in mind the reports of re-emergence of some of these diseases) compared with the potential for a 'reaction' to said vaccinations. You could perhaps argue that this viewpoint is contrary to the herd immunity afforded by vaccination; but one then arrives at the question of whether altruism has any role to play in parents taking their children for a vaccination. I'd suggest that parents would generally put their own child's health first and foremost before that of society at large despite the Utopian fantasy many would like to see and believe.

I highlighted a quote from the authors on the rate of ASDs in immunised and non-immunised younger sibling groups where the majority were not fully immunised. I imagine that to some this might be more fodder for the to-and-fro arguments about vaccination and autism and specifically that even non-immunisation status is linked to the appearance of autism. All I'll say is that bearing in mind the elevated risk of autism (and the broader phenotype) appearing in siblings of children with autism, one needs to be very cautious in applying this argument in isolation.

Finally is the question of how this current paper can further inform both autism research and immunisation policy. The scientific realisation that delays and indeed refusal is a factor in the immunisation of some siblings of children with autism is a good start. An argument could be made for example, to talk to and engage more with this parent group to ascertain what their worries are and from where they stem. I say this not to 'target' such a group and either directly or via a nudge just extol the virtues of immunisation (which I'm sure they are well aware of) and the need for immunisation, but rather find out about their personal experiences and how they informed their immunisation decisions. Demonisation and indeed labelling as 'anti-vaccine' are rarely likely to be conducive to round-table discussion. One can often learn a lot from listening and perhaps even a little clinical investigation***** (see here too ****** and an archive post on some work by Harumi Jyonouchi on SPAD).

As suggested at the start of this post, to mention immunisation and autism in the same sentence stirs up significant emotions for lots of people. I should perhaps also point out that a sizable proportion of parents questioned in the Abu Kuwaik paper did not delay or decline immunisation for siblings of children with autism. This point being illustrative of the well-trodden fact that universals with autism(s) in mind, are few and far between.

The science on vaccination and autism is very much of the opinion that population-wise there is little evidence for a link between the two factors as evidenced by papers like this one from Uno and colleagues******* and this one from Mrozek-Budzyn and colleagues********  bearing in mind contrary data********* and the problems in reliably ascertaining (non)cause and effect in a very heterogenous population. Accepting that the saga of the 1998 paper has had far-reaching consequences not just for immunisation rates and autism but also for identifying and treating various bowel conditions associated with cases of autism, one must welcome objective scientific publication and discourse on this topic outside of the emotions that it inevitably stirs up.

----------

* Abu Kuwaik G. et al. Immunization uptake in younger siblings of children with autism spectrum disorder. Autism. October 2012.

** Bazzano A. et al. Vaccine-related beliefs and practices of parents of children with autism spectrum disorders. Am J Intellect Dev Disabil. 2012; 117: 233-242.

*** Pareek M. & Pattison HM. The two-dose measles, mumps, and rubella (MMR) immunisation schedule: factors affecting maternal intention to vaccinate. Br J Gen Pract. 2000; 50: 969-971.

**** Brown KF. et al. U.K. parents' decision-making about measles-mumps-rubella (MMR) vaccine 10 years after the MMR-autism controversy: a qualitative analysis. Vaccine. 2012; 30: 1855-1864.

***** Schultz ST. et al. Acetaminophen (paracetamol) use, measles-mumps-rubella vaccination, and autistic disorder: the results of a parent survey. Autism. 2008; 12: 293-307.

****** Offit P. Vaccines and autism revisited — the Hannah Poling case. NEJM. 2008; 358: 2089-2091.

******* Uno Y. et al. The combined measles, mumps, and rubella vaccines and the total number of vaccines are not associated with development of autism spectrum disorder: the first case-control study in Asia. Vaccine. 2012; 30: 4292-4298.

******** Mrozek-Budzyn D. et al. Lack of association between measles-mumps-rubella vaccination and autism in children: a case-control study. Pediatr Infect Dis J. 2010; 29: 397-400.

********* Delong G. A positive association found between autism prevalence and childhood vaccination uptake across the U.S. population. J Toxicol Environ Health A. 2011; 74: 903-916.