Measles vaccination and inflammatory bowel disease - Controversy laid to rest?

The increasing incidence of Crohn's disease has lead to speculation about c hanges in exposures to environmental or infectious agents. Considerable att ention has focused on the role of measles infection and/or vaccination in t he pathogenesis of Crohn's disease and ulcerative colitis. Current evidence regarding the association between measles vaccination and inflammatory bowel disease (IBD) comprises analytic epidemiological studies , a case-series report and ecological studies. The first of these, a 1995 c ohort study, found an association between measles vaccination and Crohn's d isease and ulcerative colitis, but was widely questioned on methodological grounds. This was followed by a 1997 case-control study,showing no associat ion between measles vaccination and IBD. In 1998, public concern was rekind led by a report of 12 children with nonspecific colitis, ileal-lymphoid-nod ular hyperplasia, and developmental disorders largely attributed to measles -mumps-rubella vaccine, but the nature of the report limited its scientific conclusions. Two additional studies, one case-control and one cohort, then followed and neither found an association with measles vaccination. Of the several ecological studies of measles vaccine coverage or measles schedule changes, none found an association with rates of IBD. The role of measles infection in IBD has been examined more extensively wit h studies of in utero measles exposure, measles infection early in life, an d laboratory based investigations. An initial report of high rates of Crohn 's disease among pregnancies affected by measles infection was followed by negative studies. Numerous case-control and ecological studies of children with measles infections early in life have also had discordant findings. Of three recent cohort studies, two showed no relationship between infection with early measles exposure and risk for IBD, while one found an approximat e 3-fold elevation in risk. Laboratory investigations into persistent measl es infection and IBD have been contentious. While some investigators have c laimed to find persistent measles infection among patients with IBD, others , using highly sensitive polymerase chain reaction techniques, have not bee n able to replicate the findings. Recent controversy has centred on whether there is any evidence for molecular mimicry in the pathogenesis of IBD. In summary, available evidence does not support an association between measle s-containing vaccines and risk of IBD, nor between measles infection and IB D. While further research is necessary into the causal factors underlying C rohn's disease and ulcerative colitis, continued public education efforts a re needed to reassure the public about vaccine safety and to prevent declin es in vaccine coverage.