Web site: July 1998
Prescriber Update No.16:41-42
Dr Osman Mansoor, Public Health Group, Ministry of Health
A small case series has found a temporal association between autism associated with bowel disease and MMR vaccine. The evidence does not suggest that the vaccine causes autism. Public perception of risk can affect the uptake of vaccines and lead to an increase in vaccine-preventable disease. The Ministry continues to recommend immunisation, and does not consider autism a risk factor of MMR vaccine.
Doubt cast on alleged link
Unbalanced media coverage can have serious consequences
No evidence to suggest MMR vaccine causes autism
An ‘early report’ implicated measles-mumps-rubella (MMR) vaccine as a cause of autism.1 The report described 11 boys and one girl with variable bowel abnormalities and serious developmental regression (autism in nine cases). Symptoms appeared one day to two months after immunisation. The hypothesis put forward by the authors is that MMR vaccine causes inflammation or dysfunction of the intestine, increasing the absorption of non-permeable peptides, which in turn can cause serious developmental disorders.
The accompanying commentary cast doubt on the alleged link.2 The case series was subject to both selection and recall bias, the pathological findings were non-specific, there was no clear case definition and confirmatory virological studies had not been completed. The commentary also noted that although the authors had found measles virus in inflammatory bowel disease, the investigations of other researchers were negative. Indeed, the same edition of the Lancet included another study which failed to find measles virus genome in inflammatory bowel disease even though the researchers used a highly sensitive assay.
Last year the same authors claimed that MMR vaccine caused Crohn’s disease. This also received widespread media coverage despite evidence not supporting the claim. Since then, accumulating evidence against the link3 has been ignored by the media. The consequent decline in confidence in MMR vaccine has affected coverage in the United Kingdom.4
A recent editorial warns of the danger of repeating the harm caused in the United Kingdom from media reports in the 1970s about pertussis vaccine causing brain damage.5 As a result of the decline in pertussis immunisation, there were three major epidemics over 12 years causing over 300,000 notifications and at least 70 deaths.
On 23 March 1998, the British Medical Research Council held a meeting of experts who concluded that the available evidence does not indicate a link between measles, measles vaccine or MMR immunisation and either Crohn’s disease or autism. Two other studies have failed to show any association.6,7
The Ministry of Health also considers there is no evidence to suggest that there is a risk of autism from MMR vaccine. Information contained in the Immunisation Choices booklet still represents an accurate description of the risks of immunisation compared to the disease. High immunisation coverage is critical to disease control, especially at the tail-end of a measles epidemic that was limited through immunisation.