Are Vaccines Safe? (Part 3)

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Perhaps the most common negative side-effect advanced by anti-vaccination advocates is autism. One reason for the widespread acceptance of this link comes from a paper published in the British journal The Lancet. The paper titled “Ileal-Lymphoid-Nodular hyperplasia, Non-Specific Colitis, and Pervasive Developmental Disorder in Children” garnered boundless media coverage. One only has to look at the pedigree and number of authors to see why people were so impressed with the article. The authors of the article are: Dr AJ Wakefield, SH Murch, MB, A Anthony, MB, J Linnell, PhD, DM Casson, MRCP, M Malik, MRCP, M Berelowitz, FRCPsych, AP Dhillon, MRCPath, MA Thomson, FRCP, P Harvey, FRCP, A Valentine, FRCR, SE Davies, MRCPath, JA Walker-Smith, FRCP. We will simply use the first author’s name for simplicity.

Wakefield et al’s paper tried to show a link between the measles-mumps-rubella (MMR) vaccine and autism. There were flaws in the paper and subsequent publications contradicted its findings. The paper was written in 2008 and retracted by 2010.

Reasons for Retraction

One of the first blows to Wakefield et al. was a paper titled “Autism and Measles, Mumps, and Rubella Vaccine: No Epidemiological Evidence for a Causal Association” written by Taylor B, Miller E, Farrington CP, Petropoulos MC, Favot-Mayaud I, Li J, Waight PA. This paper refuted the findings of Wakefield’s paper. Here are their findings:

We identified 498 cases of autism (261 of core autism, 166 of atypical autism, and 71 of Asperger’s syndrome). In 293 cases the diagnosis could be confirmed by the criteria of the International Classification of Diseases, tenth revision (ICD10: 214 [82%] core autism, 52 [31%] atypical autism, 27 [38%] Asperger’s syndrome). 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. There was no temporal association between onset of autism within 1 or 2 years after vaccination with MMR (relative incidence compared with control period 0.94 [95% CI 0.60-1.47] and 1.09 [0.79-1.52]). Developmental regression was not clustered in the months after vaccination (relative incidence within 2 months and 4 months after MMR vaccination 0.92 [0.38-2.21] and 1.00 [0.52-1.95]). No significant temporal clustering for age at onset of parental concern was seen for cases of core autism or atypical autism with the exception of a single interval within 6 months of MMR vaccination. This appeared to be an artifact related to the difficulty of defining precisely the onset of symptoms in this disorder.

If Taylor et al. findings weren’t explicit enough; the authors offers an interpretation of their findings which says, “Our analyses do not support a causal association between MMR vaccine and autism. If such an association occurs, it is so rare that it could not be identified in this large regional sample.”

Their findings are significant, in contrast to Wakefield’s paper, with regard to the number of cases they examined because Wakefield et al. only examined 12 children.

In 2001 another paper published in The Journal of the American Medical Association (JAMA) titled “Time Trends in Autism and in MMR Immunization Coverage in California” seriously called into question the findings of Wakefield et al. study. The paper’s authors are: Loring Dales, MD; Sandra Jo Hammer, RN, PHN and Natalie J. Smith, MD, MPH. They found:

Essentially no correlation was observed between the secular trend of early childhood MMR immunization rates in California and the secular trend in numbers of children with autism enrolled in California’s regional service center system. For the 1980-1994 birth cohorts, a marked, sustained increase in autism case numbers was noted, from 44 cases per 100 000 live births in the 1980 cohort to 208 cases per 100 000 live births in the 1994 cohort (a 373% relative increase), but changes in early childhood MMR immunization coverage over the same time period were much smaller and of shorter duration. Immunization coverage by the age of 24 months increased from 72% to 82%, a relative increase of only 14%, over the same time period.

The study plainly concludes, “[t]hese data do not suggest an association between MMR immunization among young children and an increase in autism occurrence.”

JAMA published yet another paper titled “Association between Thimerosal-Containing Caccine and Autism” by Anders Hviid, MSc; Michael Stellfeld, MD; Jan Wohlfahrt, MSc. The results were the same:

During 2 986 654 person-years, we identified 440 autism cases and 787 cases of other autistic-spectrum disorders. The risk of autism and other autistic-spectrum disorders did not differ significantly between children vaccinated with thimerosal-containing vaccine and children vaccinated with thimerosal-free vaccine (RR, 0.85 [95% confidence interval {CI}, 0.60-1.20] for autism; RR, 1.12 [95% CI, 0.88-1.43] for other autistic-spectrum disorders). Furthermore, we found no evidence of a dose-response association (increase in RR per 25 µg of ethylmercury, 0.98 [95% CI, 0.90-1.06] for autism and 1.03 [95% CI, 0.98-1.09] for other autistic-spectrum disorders).

Hviid et al. conclude “[t]he results do not support a causal relationship between childhood vaccination with thimerosal-containing vaccines and development of autistic-spectrum disorders.”

The second pillar fell when 10 of the 12 authors of the Wakefield paper retracted their interpretation of the data. I take this to be one of the most significant cracks in the paper’s infrastructure.

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