Measles, MMR, and autism: the confusion continues

Abstract

The WHO estimated the number of measles cases for 1998 as 30 million worldwide with 888 000 measles-related deaths. In developing countries about 10% of all deaths in children under 5 years are measles related. Sad figures considering that measles has been a vaccine-preventable disease for more than three decades. In 1990, the World Summit for Children adopted a goal of vaccinating 90% of children by 2000; despite this undertaking, global coverage actually declined from 79% in 1997 to 72% in 1998. Vaccine coverage varies widely, and 16 countries reported coverage below 50% in 1998. One such country is Afghanistan, where a measles epidemic is now raging with many deaths (see p 1439). In more-developed countries, measles is often regarded, erroneously, as a mild disease-a view belied by the fact that in the USA, in a measles outbreak of about 55 000 cases from 1989 to 1991, over 120 people died. Complications include bronchopneumonia, diarrhoea, encephalitis, and subacute sclerosing panencephalitis (SSPE), which leads to death and occurs in 1 out of 8000 children who become infected with measles before their second birthday. SSPE cases have fallen dramatically since the introduction of measles vaccine. A huge blow to the efforts of measles eradication was dealt when 2 years ago, at a press conference, Andrew Wakefield from the Royal Free Hospital, UK, argued that because of uncertainty about its safety, the measles, mumps, and rubella (MMR) vaccine should be withdrawn and the components given separately. He made this claim—not shared by his coinvestigators—on the grounds that there was an association between autism and intestinal abnormalities in 12 children and a possible relation—as recalled by some parents—with MMR vaccination (Lancet 1998; 351: 637–41). Well-founded criticisms of both the study and its interpretation by Wakefield followed, and a different research group from the same institution published epidemiological evidence contradicting this alleged association (Lancet 1999; 353: 2026–29). On April 3, a report from a subgroup of the British Medical Research Council, led by Alan McGregor of King's College London, concluded that “between March, 1998, and September, 1999, there had been no new evidence to suggest a causal link between MMR and inflammatory bowel disease/ autism”. In a new twist, Wakefield's crusade fuelled further anxiety among parents when he and John O'Leary, director of pathology at Coombe Women's Hospital, Dublin, Ireland, presented unpublished data to the US Senate's congressional oversight committee in Washington on April 6. The hearing was called by the chairman, Dan Burton, an Indiana Republican, whose grandson has autism and visited the Royal Free Hospital in November last year. At the hearing, six parents of children with autism gave moving testimonies of their children's illness. Scientific evidence was presented by six chosen “experts”. According to Wakefield's testimony, he has now studied more than 150 children with “autistic enterocolitis”—an unproven association had become a disease—and a detailed analysis of the first 60 cases is to be published in the American Journal of Gastroenterology later this year. Wakefield presented uninterpretable fragments of results only and concentrated on refuting studies that had contradicted his findings. His conclusions were surprisingly non-committal: “the virological data indicate that this may be measles virus in some children”; he added that it would be imprudent to interpret the temporal relationship with MMR as a chance finding, in the absence of thorough investigation. O'Leary explained that gut-biopsy material from 24 of 25 children with autism was positive for measles virus compared with one of 15 controls, and that this material was presented to him by Wakefield using “blinded protocols”. Since the controls are not further described and the details of these findings remain unpublished, this evidence raises far more questions than it answers. Autism is a poorly understood neurodevelopmental-disease spectrum with a heart-breaking personal story behind every case. But parents of such children have not been served well by these latest claims made well beyond the publically available evidence. A congressional hearing, like a press conference, is no place to make controversial scientific assessments. And if scientists question the safety of vaccines without making their evidence fully transparent, harm will be done to many more children than they purport to protect.