Measles-Mumps-Rubella Vaccine Safe

October 27, 2005

A subject of ongoing controversy, the mumps-measles-rubella (MMR) vaccine has been deemed safe by an international team of investigators, according to a report in MedPage Today on 19 October.

The MMR vaccine has questionably been linked with autism and Crohn's disease, raising concerns among parents about having their children immunized with MMR. The findings of this review were published in the Cochrane Library on 19 October 2005.

"In particular we conclude that all the major unintended events, such as triggering Crohn's disease or autism, were suspected on the basis of unreliable evidence," said Vittorio Demicheli, MD, of the Servizo Sovrazonale di Epidemiologia and colleagues as part of a systematic review from the Cochrane Collaboration.

"Mumps, measles and rubella are serious diseases that can lead to potentially fatal illness, disability and death," wrote Dr. Demicheli and colleagues. "Measles, mumps and rubella are particularly prevalent in developing countries where vaccination programs are inconsistent and the mortality rate from disease is high. In developed countries, however, mumps, measles and rubella are now rare, due to large-scale vaccination programs."

Original Concerns

The MMR vaccine was first used in the US in the 1970s and is now routinely used in over 90 countries. The vaccine's safety came into question because of a small study (only 12 patients) published in The Lancet in 1998. The paper has since been retracted by 10 of the 13 original authors, but when published it triggered an international scare resulting in reduced use of the vaccine.

In an effort to address the controversy surrounding the vaccine, members of The Cochrane Collaboration set out to review evidence of the vaccine's effectiveness and evidence of associated adverse events.

Review of Data

Of a total 139 studies identified, 31 were determined to be of sufficiently high quality to rule out error or bias. The 31 studies included comparative prospective or retrospective trials that tested MMR's effects of MMR against those of placebo, no treatment, or a combination of measles, mumps and rubella antigens on healthy children up to age 15 years.

Data analysis showed that the MMR vaccine was associated with a higher rate of irritability, a lower rate of upper respiratory-tract infections and similar rate of other adverse effects, compared to placebo. Positive associations between MMR and benign thrombocytopenic purpura, parotitis, joint and limb complaints and febrile convulsions within two weeks of vaccination were also found.

Also, versions of the MMR vaccine containing the 'Urabe' strain of mumps, but not the more widely used 'Jeryl Lynn' strain, were associated with aseptic meningitis.

However, no credible evidence of an association between the MMR vaccine and Crohn's disease, ulcerative colitis or autism was found.

The authors noted that, although they did not identify MMR effectiveness studies that had clear clinical endpoints, the overwhelming evidence that the targeted diseases had been eliminated or radically reduced through mass immunization campaigns is proof that the vaccine achieves its primary aim.

"The safety record of MMR is possibly best attested by its almost universal use," Dr. Demicheli and colleagues wrote, according to MedPage Today. "Its evaluation cannot be divorced from its effectiveness and the importance of the target diseases. As such, MMR remains an important preventive global intervention."

Measles Outbreak in the US

In a related story, a large outbreak of measles in Indiana in May-June 2005 demonstrated the potential effects of measles on a group of unvaccinated individuals, according to a report by Reuters on 27 October.

This outbreak and the serious cases of measles that followed would have been prevented if parents and doctors had followed longstanding measles vaccination guidelines, according to researchers from the Centers for Disease Control and Prevention who reported the events in their Morbidity and Mortality Weekly Report.

The source of the outbreak in Indiana, which occurred over a 4-week period in May and June, was an unvaccinated female teenager who had visited Romania during a major measles outbreak. Soon after her return to Indiana, 34 measles cases arose, most of which involved children whose parents had declined to have them vaccinated with the MMR vaccine.

All of the patients recovered, although three were hospitalized, according to Reuters.

Among the measure taken by local health departments in Indiana, Ohio and Illinois to prevent further spread of the outbreak were voluntary patient isolation, administration of vaccine and immunoglobulin to susceptible contacts and verifying healthcare workers' immune status.

"The Indiana outbreak could have been prevented by adherence to longstanding Advisory Committee on Immunization Practices recommendations calling for measles vaccination of 1) international travelers, 2) children, and 3) healthcare workers," the report concludes.

Sources:
MMR Vaccine is Safe, International Team Affirms, MedPage Today, 19 October 2005.
Cochrane Library publishes the most thorough survey of MMR vaccination data, MedicalNewsToday.com, 22 October 2005.
Measles outbreak shows vaccination value, Reuters, 27 October 2005.

Posted: October 2005


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