Timing of regressive autism
Related to introduction of MMR
Testimony to the House Government Reform Committee by Andrew J. Wakefield, M.D.
If MMR vaccine is causally related to autism and autistic enterocolitis, then there should have been an increase in the numbers of cases of autism following the introduction of MMR vaccine in different countries. Moreover, since MMR was introduced into different countries at different times, the effect should be one of similar temporal trends in different countries, with any increase corresponding with the introduction of MMR.
Superimposing the data for the US and the UK, analyses described above, identical time trends are seen, with a delay in the rise in the UK that corresponds to the later introduction of the MMR vaccine in 1988: Temporal trend for autism: US and UK
It is important to note that the UK and the US use exactly the same diagnostic criteria for autism and yet there is a 10-year delay in rise in the number of cases. These changes are very unlikely to reflect artefacts due to changing diagnostic criteria. This is confirmed by reviewing the temporal trends for autism and learning disabled children in the state of Illinois from 1991-1997.
Taylor et al tested the hypothesis that there should be no temporal clustering of first parenteral concerns with measles, mumps, and rubella (MMR) vaccination. They identified a statistically significant excess risk by 6 months after MMR, which they dismiss, post hoc, as indicating parential recall bias. Had this been the case it should have been seen in both of their vaccine groups--those receiving MMR and those receiving any measles-containing vaccine. The excess risk was seen only in the MMR group; this is a fundamental flaw. In 1998 the expected numbers of newly diagnosed autistic children in California should have been 105-263 cases, according to DSM-IV; the actual figure was 1685 new cases. The temporal trend in north-west London is almost identitical, although the rise is delayed by about 10 years. The two countries use the same diagnostic criteria. The sequential trends are consistent with the timing of introduction of MMR to both regions. * Data from Departmental of Developmental Services, 1987-98 (www.dds.ca.gov ).
However, it pales into insignificance compared with their failure to declare the fact of an MMR catch-up campaign that was initiated in 1988 with the introduction of this vaccine. This campaign was targeted at children, whatever their age, who presumably had not received monovalent mumps or rubella vaccine whatever their exposure status. As such it was a novel and, in terms of safety, untested policy. On the basis of Taylor and colleagues' inclusion criteria, and taking account of the catch-up campaign, then those first birth cohots who actually received MMR (circa 1986) were precisely those in whom a doubling of the numbers of cases of autism were seen.
Thereafter these numbers continue to increase strikingly. Omission of this essential fact--the catch-up campaign--requires explanation lest it be misconstrued.Measles/autism time lines - The Lancet, September 11, 1999, p. 950
Opposing view - not related to introduction of MMR
Because the incidence of autism among 2 to 5 year olds increased markedly among boys born in each year separately from 1988 to 1993 while MMR vaccine coverage was over 95% for successive annual birth cohorts, the data provide evidence that no correlation exists between the prevalence of MMR vaccination and the rapid increase in the risk of autism over time. The explanation for the marked increase in risk of the diagnosis of autism in the past decade remains uncertain.
There was a steady increase in cases by year of birth with no sudden "step-up" or change in the trend line after the introduction of MMR vaccination. There was no difference in age at diagnosis between the cases vaccinated before or after 18 months of age and those never vaccinated.