MMR is safe – so why are many still scared of it?
The good news: a study found no persistent trace of measles in autistic children after MMR. The bad news: it may not be enough to allay public fears.
An authoritative study has failed to confirm that children with autism carry persistent traces of measles virus following MMR immunisation.
In 2002, a team led by Professor John O’Leary in Dublin claimed to have found measles virus genome sequences in more than 80 per cent of gut biopsy specimens from autistic children (provided by the former Royal Free researcher Andrew Wakefield). In 2004, Dr Wakefield’s Florida colleague Jeff Bradstreet claimed to have found similar levels of measles virus in cerebrospinal fluid (CSF) specimens. Though these findings were considered unconvincing by scientific authorities, they were widely believed by parents of autistic children, and played an important role in sustaining the campaign against MMR.
Now the notion that MMR causes lingering measles infection in children with autism has been authoritatively refuted. In a study published in the current Journal of Medical Virology, a team led by London-based virologist Muhammad Afzal, and including the Edinburgh autism specialist Anne O’Hare, set out to replicate the methods used by Professor O’Leary (QRT-PCR TaqMan) and also used a more sensitive test (RT-PCR-nested PCR assay) (1). These methods have the potential to detect measles virus RNA transcripts down to single figure copy numbers. Considering it unethical to inflict colonoscopy or lumbar puncture on autistic children for research purposes, the authors used blood specimens taken for other clinical investigations from 15 children who presented sequentially to an autism diagnostic service in the south east of Scotland. The sample included 12 boys and 3 girls; 10 had shown signs of regression in their second year. All had received MMR.
The authors could find no measles-virus specific genetic fragments by any method in any case, using assays targeting multiple genomic regions under various experimental formats to improve detection rates. However, they found that all the patients had detectable levels of anti-measles antibodies. They observed that ‘it therefore seems reasonable to conclude that, after provoking immunity in the vaccine recipients, measles virus was eliminated from the blood by the host defence system, as expected with normal healthy children’.
These results suggest that the high rates of measles virus traces found in Professor O’Leary’s laboratory were the results of cross-contamination of samples and/or false positive scoring.
Dr Afzal’s study is good news for parents who have come to fear that by giving their children MMR they may have contributed to their development of autism. It is particularly good news for parents who may have been misled by results from Professor O’Leary’s lab into believing the MMR-autism theory. It is also good news for parents facing decisions about giving their children MMR: within weeks of the first death from measles in the UK for 14 years, we have further strong evidence for the safety of MMR.
This study is, however, bad news for Dr Wakefield and Professor O’Leary. In his now notorious (and partly retracted) 1998 Lancet paper, Dr Wakefield invited further researches into his MMR-autism hypothesis in the spheres of epidemiology and virology. When numerous epidemiological studies failed to support his thesis, he decided that such methods were not suitable to detect the small number of autism cases linked to MMR (though his supporters continued to blame MMR for a supposed ‘epidemic’ of autism).
Professor O’Leary is reported to have received around £800,000 from the anti-MMR litigation for carrying out tests for measles virus that have now been discredited by a rigorous independent virological study (2). As Dr Afzal and colleagues put it, ‘in summary, the data presented in this study failed to verify the finding of previous studies that predicted persistence of measles virus in autistic children with developmental regression’.
For all its scientific rigour, the Afzal paper will have a limited effect in allaying the anxieties provoked by the campaign against MMR. It is not clear why it has taken so long for this relatively straightforward study to be completed: it is now eight years since Dr Wakefield’s notorious Lancet paper and four years since O’Leary’s research was published. It is also unfortunate that it is based on such a small number of cases – scarcely more than were included in Wakefield’s original study. Given that the Wakefield/O’Leary research was based on children with autism and bowel complaints, it would have strengthened the Afzal study if it had limited its subjects to similar children, even if they had to be recruited from a number of centres.
The low key presentation of this study – published in an obscure scientific journal with little wider publicity – is also characteristic of the official response to the campaign against MMR. All in all, it is a case of ‘too little, too late’. It is no wonder that, despite the scientific weakness of his case, Wakefield has been so successful in the battle for public opinion.
(1) M.A. Afzal, L.C. Ozoemena, A. O’Hare, K.A. Kidger, M.L. Bentley, P.D.
Minor. Absence of detectable measles virus genome sequence in blood of autistic children who have had their MMR vaccination during the routine childhood immunization schedule of UK, Journal of Medical Virology, 2006; 78: 623-630.
(2) Brian Deer, Fresh doubts cast on MMR study data, Sunday Times, 25 April 2004
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