Editor—Metcalf concludes that the scientific evidence does not support a causal link between measles virus and Crohn’s disease.1 Though few readers of the BMJ are likely to disagree with her appraisal of the science, parental concern about the safety of the vaccine remains high fuelled by continuing media interest in this controversial topic. More worrying is the recent decline in MMR vaccine coverage2 and evidence which suggests that most practice nurses would not give their own child a second dose of MMR vaccine because of concerns about vaccine safety.3
One of the claims made by the leading proponent of the hypothesis that measles vaccine causes Crohn’s disease is that there has been a “dramatic escalation” in paediatric cases in the wake of the 1994 national measles-rubella vaccination campaign targeted at school aged children.4 We have monitored hospital discharge diagnoses for Crohn’s disease (ICD-9 code 555 until March 1995, ICD-10 code K55 from April 1995) in children aged 5-16 years before and after the campaign using computerised hospital episode statistics from all districts in England (figure). Children with new cases of Crohn’s disease are almost always admitted to hospital, and this is a well established method of monitoring trends in incidence of the disease. Repeat admissions in the same child were identified by matching sex, date of birth, and postcode.
No increase was evident in either first admissions or all admissions for Crohn’s disease since the campaign. Although the latent period between exposure to measles-rubella vaccine and alleged onset of Crohn’s disease was not stated by Wakefield, our data exclude an effect within the first 16 months. This technique can be reapplied annually, allowing the cohort immunised in the 1994 campaign to be followed longer term.
We are not aware of any published evidence to support the hypothesis that re-exposure to measles vaccine can provoke the onset of Crohn’s disease. However, evidence which counters unsubstantiated allegations may help health professionals reassure themselves, as well as concerned parents, about the safety of measles vaccine given as a second dose in combination with another live viral vaccine.
Figure.
Hospital admissions for Crohn’s disease, January 1992 to March 1996
References
- 1.Metcalf J. Is measles infection associated with Crohn’s disease? BMJ. 1998;316:166. doi: 10.1136/bmj.316.7126.166. . (17 January.) [DOI] [PMC free article] [PubMed] [Google Scholar]
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- 3.Roberts N. Why are practice nurses scared of MMR2? GP Medicine January 23 1998.
- 4.Wakefield AJ. National Vaccine Information Centre’s first international public conference on vaccination, Alexandria, VA, September 13-15 1997. Vienna: VIC; 1997. [Google Scholar]



