Vaccination for Haemophilus Influenzae Type b is not Associated with a Risk of Diabetes Mellitus
abstract & commentary
Synopsis: Based on new studies, it appears unlikely that H. influenzae type b vaccination or its timing causes type 1 diabetes mellitus in children.
Source: Karvonen M, et al. BMJ 1999;318:1169-1172.
Because most children receive various vaccines on many occasions during their first five years of life, it is not at all surprising that a variety of conditions and events may occur in proximity to a childhood immunization. A question in most of these cases of vaccination-disease associations is whether the vaccine actually was causally related to the condition or was only coincidental. There have been a number of linkages of childhood immunizations and specific diseases that have led to public concern (recently an alleged relationship between hepatitis B immunizations and multiple sclerosis prompted a moratorium on HpB immunizations in France). Damage to the pancreatic beta cells leading to type 1 diabetes is believed to be caused by environmental factors including infections and possibly immunizations.
In 1988, the vaccine for H. influenzae type b was given to virtually all children born in Finland as part of a nation efficacy trial. The design of the trial was that children born between 1985 and 1987 who were born on odd-numbered days received the conjugate Hib vaccine at 3, 4, and 6 months of age followed by a booster at 14-18 months of age. Children born on even-numbered days were a control group and received Hib vaccine at 24 months of age only. Of interest is the fact that Finland has the highest incidence of type 1 diabetes mellitus in children younger than 14 years of age in the world, and its incidence has been increasing by 2-3% per year since the 1940s. Classen and Classen described an apparent accelerated increase in the incidence of type 1 diabetes in children after the national program for Hib immunization began in 1988 and have speculated that there may be a causal association.1,2 However, because of the near universality of immunizations in infancy and childhood and the relative rarity of diabetes, an enormous database of appropriate data is necessary to generate statistically convincing conclusions.
Karvonen and associates from the Diabetes and Genetic Epidemiological Unit of the National Public Health Institute in Helsinki compared the cumulative incidence and risk of type 1 diabetes in three cohorts of Finnish children: those born 24 months before the start of the national Hib immunization program was begun; those in the 1988 trial cohort who received Hib vaccine at 3 months of age followed by a later booster; and the control cohort from the trial who were vaccinated at 24 months only. The data were obtained from a nationwide hospital discharge registry. There were no differences between the incidence of type 1 diabetes in the three groups. Karvonen et al conclude that it is unlikely that H. influenzae type b vaccination or its timing causes type 1 diabetes mellitus in children.
Comment by Howard Pearson, MD, FAAP
It is hoped that similar rigorous analysis will be used to establish or disprove causal relationships between beneficial procedures such as childhood immunizations and rare pediatric conditions. In fact, a recent article showed no association between autism and MMR immunizations.3 (Dr. Pearson is Professor of Pediatrics, Yale University School of Medicine.)
References
1. Classen JB, et al. Infect Dis Clin Pract 1997;6:449-454.
2. Classen JB, Classen DC. BMJ 1998;318:193.
3. Talor B, et al. Lancet 1999;353:2026-2029.
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