Cochrane meets controversy: Vaccines for measles, mumps, and rubella

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A lot has already been written on the subject of the measles-mumps-rubella (MMR) vaccine in children. A lot, a lot, a lot. But many countries around the world are currently experiencing another measles outbreak, and public opinion on the safety and necessity of the MMR vaccine continues to be divided by strongly-held, opposing beliefs.

So, we turned to a Cochrane review on the safety and effectiveness of the MMR vaccine for an exhaustive look at the evidence from 64 studies involving approximately 14,700,000 children (Demicheli, 2012), and according to the review authors,

“Existing evidence on the safety and effectiveness of MMR vaccine supports current policies of mass immunisation aimed at global measles eradication and in order to reduce morbidity and mortality associated with mumps and rubella.”

These conclusions are based on the ≥95% effectiveness of the vaccine in preventing clinical and laboratory-confirmed measles cases in preschool children, school-aged children, and adolescents; 92% and 95% prevention of secondary measles cases with one and two doses, respectively; and 64-88% prevention of mumps cases, depending on the strain of vaccine used. No studies of the effectiveness of the MMR vaccine in protecting against rubella were found.

There are rare harms associated with the MMR vaccine, including aseptic meningitis (Urabe and Leningrad-Zagreb mumps strains), febrile seizure (Moraten, Jeryl Lynn, Wistar RA, and RIT 4385 strains), and fever, convulsions, and acute or idiopathic thrombocytopenic purpura (vaccine composition not described). However, there is no scientific evidence to suggest that MMR is associated with: autism, asthma, leukemia, hay fever, type 1 diabetes, gait disturbance, Crohn’s disease, demyelinating diseases, or bacterial or viral infections.

These results probably don’t come as much of a surprise to those on the front lines, caring for children. But in the face of controversy, being armed with the evidence can’t hurt.

According to Dr. Joan Robinson, Divisional Director of Pediatric Infectious Disease at the University of Alberta, “Most people under 50 have never seen a case of measles and are not aware that it is a miserable disease with about 5 to 10% of infected children requiring hospitalization and 1 in 1,500 children having brain involvement. The harms that have been linked to the vaccine are all much more common with measles infection than they are with vaccine. Until recently, parents thought that they could rely upon “herd immunity,” meaning that if most other children were immunized, their unimmunized child would not be exposed to measles. However, this has changed as the number of unimmunized children has increased. The recent US outbreak that started in Disneyland demonstrates how very infectious the measles virus is and proves that “It’s a Small World After All.”

Reference:

Demicheli V, Rivetti A, Debalini MG, Di Pietrantonj C. Vaccines for measles, mumps and rubella in children. Cochrane Database of Systematic Reviews 2012, Issue 2. Art. No.: CD004407. DOI: 10.1002/14651858.CD004407.pub3. See summary here.

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