Measles Vaccination and Inflammatory Bowel Disease in Japanese Children

Abstract

To the Editor: The report of Thompson et al.(1) suggests an association between measles vaccination and inflammatory bowel disease (IBD), particularly Crohn's disease (CD). Japan is a country in which the prevalence of IBD is far lower than in European countries and in the United States, although a rise has become apparent in adults in recent years (2). It is therefore important to report the incidence rates of IBD in Japanese children and performance rates of measles vaccination in Japan. Mass vaccination against measles was introduced in 1978 in Japan, and the nationwide performance rate has been between 70% and 90% (3). The efficacy rate of the vaccination was 96.2% to 97.8% (3), and the vaccination program has been thought to be successful. Measles, mumps, and rubella vaccine was introduced in April 1989, but it had to be suspended because of a high complication rate of meningitis in April 1993, and it has not been reinstituted. A nationwide epidemiologic survey of ulcerative colitis (UC) and CD in children less than 16 years old was carried out from 1979 to 1993(4). The total number of the patients collected was 578 with UC and 260 with CD by 1993, whereas the total population less than 16 years old was 22,400,000 to 29,000,000 in each year of this period. The number of new UC and CD patients occurring in each year was almost the same after 1979; however, new UC patients per 100,000 increased in 1993 and new CD patients per 100,000 in 1992 and 1993, after having remained at a plateau for a decade after the time of introduction of measles vaccination. Incidence rates of UC per 100,000 were 0.08 in 1979 (population less than 16 years old: 29,081,000), 0.085 in 1980 (28,968,316), 0.12 in 1985 (27,647,604), 0.11 in 1990 (24,395,897), 0.1 in 1992 (23,137,200), and 0.18 in 1993 (22,407,000). Rates of CD were 0.04 in 1979, 0.05 in 1980, 0.06 in 1985, 0.03 in 1990, 0.05 in 1991, 0.10 in 1992 and 0.12 in 1993. Magnitudes of increased incidence rates from 1979 to 1993 are double in UC and triple in CD. The age at onset was distributed throughout all ages from 0 to 15 years in both disorders, but more patients 8 years old and older were seen with UC and more 10 years old and older with CD. From results of this survey, it could be proposed that Japanese do not have a genetic predisposition to IBD; nonetheless, a causal role for various environmental factors should be taken into consideration in describing the etiology of this disorder in Japanese people. If measles vaccine increases the risk of developing CD but not UC, the increases of CD and UC in Japan a decade after introduction of the vaccination can not be explained solely by this factor. Another explanation for this increase may be changes in life style, including the change in diet from traditional Japanese foods to European or North American foods; delayed exposure to enteric infections(5); and low infant mortality(6). We thank Dr. H. Urashima for kind permission to use his data describing IBD in Japanese children. Y. Yamashiro *J. A. Walker-Smith T. Shimizu S. Oguchi Y. Ohtsuka Department of Paediatrics; Juntendo University School of Medicine; Tokyo, Japan;*University Department of Paediatric Gastroenterology; Royal Free Hospital; London, United Kingdom