WEDNESDAY, March 31, 2004 (HealthDayNews) -- Danish researchers have concluded that childhood vaccinations do not cause type 1 diabetes.
Given the increased incidence of the disease in recent years in developed countries, an association between type 1 diabetes and routine childhood vaccinations has been suggested. Few analytic studies have directly addressed the issue, however.
The current study, which appears in the April 1 issue of the New England Journal of Medicine, seems to definitively refute that line of thinking.
While acknowledging that "it is often easier to come up with a hypothesis than it is to refute it," the authors of the study, Anders Hviid and Dr. Mads Melbye of the Statens Serum Institute in Copenhagen, Denmark, say "both the design and size of our study makes our result very robust. We found absolutely no indication that childhood vaccines cause type 1 diabetes."
Furthermore, they add, "Our study is the largest and most detailed to date -- utilizing the unique, complete Danish population registries -- and it is unlikely that a similar or larger study could be conducted anywhere else."
Hviid and Melbye looked at the relationship between type 1 diabetes and routinely administered childhood vaccinations among all children born in Denmark between 1990 and 2000. They correlated records on vaccinations and on diagnosis of type 1 diabetes, with children's personal identification numbers.
Between 1990 and 2001, Denmark's national policy was to vaccinate children against pertussis, measles, mumps, rubella, diphtheria, tetanus, polio and Haemophilus influenzae type B (Hib).
In all, type 1 diabetes was diagnosed in 681 children. The rate of type 1 diabetes among children who had received at least one dose of Hib vaccine compared to unvaccinated children was almost identical. The same held true for the diphtheria, tetanus, and inactivated polio combination vaccine; for the diphtheria, tetanus, acellular pertussis and inactivated polio booster vaccine; for whole-cell pertussis; for the measles, mumps and rubella combination vaccine; and for oral polio vaccine.
"Overall, there were no more cases of type 1 diabetes among vaccinated children compared with unvaccinated children," the authors point out.
Even in those children who were genetically predisposed (those who had a sibling with the disease), type 1 diabetes was not significantly associated with vaccination.
And there didn't seem to be a rash of diagnoses two to four years after vaccinating. "There were no clusters of type 1 diabetes in the period following vaccination," the authors state.
Hviid and Melbye also feel these results can be extrapolated to other countries. "With respect to type 1 diabetes, the Danish population is a relatively high-risk population, and thus our results can be extrapolated and are relevant for other countries," they say.
Of course, different vaccines have, over the past 40 years, been associated with other adverse effects, an accompanying editorial points out. For instance, a rotavirus vaccine was recalled because of an association with an increased rate of intussusception, which is when part of the bowel slips into another.
Overall, though, the benefits outweigh the risks, both the study and perspective authors point out.
"This study will, one hopes, be the last one that it necessary to disprove an association between immunization and diabetes," writes Dr. Lynne L. Levitsky of Massachusetts General Hospital in Boston. "The scientific community should now move on to the most important tasks: identifying the genetic, immunologic, and environmental phenomena that are actually responsible for the development of diabetes and finding the means to prevent and treat this chronic disorder."
"Vaccination is one of the most successful health interventions ever," Hviid and Melbye say. "We believe that research into vaccine safety should be given high priority, if not for purely scientific reasons, then to maintain public and professional confidence in vaccination. Unsupported hypotheses questioning vaccine safety increases anti-vaccination sentiment and jeopardizes vaccination programs worldwide."