Concerns about the safety of MMR arose in 1998, when the British medical journal The Lancet published a study linking the injections with the onset of autism and Crohn’s disease in twelve children. In the UK, the study triggered a collapse in vaccination rates and subsequent measles outbreaks.
Since that time, intensive studies of MMR safety have been conducted around the world, and they have not confirmed the link between MMR and autism or bowel disease. The new comprehensive review of studies adds to the weight of evidence supporting the safety and efficacy of MMR. “MMR remains an important preventive global intervention,” conclude the authors.
Demicheli and coauthors analysed 139 studies of children up to age 15, eventually selecting 31 of the highest-quality reports for review. Ten of these focused on long-term adverse effects and ranged in size from several hundred participants to more than 500,000.
The review confirmed that the combined vaccine may cause expected short-term effects such as irritability, fever, rash and joint stiffness. Very rarely, more serious side effects such as bleeding disorders and seizures may occur. Nevertheless, “No credible evidence of an involvement of MMR with either autism or Crohn’s disease was found,” say the authors.
The quality of the studies was not perfect, concedes Demicheli. Cochrane reviews generally focus on studies that compare an experimental group to a control group that receives different treatment.
When broad vaccination programs have been underway for many years, there are no people to serve as a comparison group. Yet, he says, “If you keep finding consistent results across different settings, across different study designs, it’s reasonable that what you have found is true.”
MEDICA.de; Source: Health Behaviour News Service