ATLANTA - A recent report that appeared on the evening news suggested a link between the administration of recommended childhood vaccines and the development of diabetes - and most likely resulted in an increase in calls to pediatricians' offices from panic-stricken parents.
According to the report on ABC World News Tonight routine childhood vaccines could increase or de crease a child's risk of developing juvenile onset diabetes, also known as diabetes type 1 or insulin-dependent diabetes mellitus, depending on when the vaccines were administered.
The Centers for Disease Control and Prevention (CDC) released a response taking issue with the televised report. The CDC report said that no evidence has established a link between vaccination and diabetes.
Frank DeStefano, MD, with the CDC Vaccine Safety and Development Activity, said there are clearly no verified findings to show that vaccines cause diabetes or increase the risk of developing diabetes in humans, the original research raising the hypothesis is questionable at best.
"There is no evidence to say that there is an increased risk of developing diabetes if immunizations are given at 2 months or older - even in the animal models," he said. "I don't know where that kind of reasoning came from or the idea to explore that there might be an increased risk."
The only evidence suggesting a possible increase in risk are studies by John B. Classen, MD. He suggested that if certain vaccines are given at birth, they may decrease the occurrence of diabetes. However, his research also indicated that the occurrence of diabetes increases if the initial vaccination is given after a child is 2 months old.
Classen started a company to commercialize his research findings, according to Robert T. Chen, MD, chief of Vaccine Safety and Development Activity at the National Immunization Program. DeStefano and others at the CDC question these findings because Classen's theory is based on animal experiments. In addition, he compared diabetes rates among countries with different immunization schedules, which may be comparing apples to oranges. Finally, many of the experiments used anthrax vaccine, which is rarely used in children. The comparisons between countries involved bacille Calmette-Guérin vaccine, which is rarely used in the United States, and smallpox vaccine, which is no longer used in this country.
"It's difficult to interpret those kinds of results because countries differ in a variety of factors besides their immunization schedules. Their genetic compositions differ, other environmental exposures are different and even adherence to the recommended schedule may not be complete," he said.
Classen has also noted a rise in diabetes among Finnish children younger than age 10 who received measles-mumps-rubella (MMR) vaccine. The rise was noted in 1983, and an MMR immunization program was launched in 1982. The rise in diabetes cases was not seen unvaccinated 10 to 14 year-olds.
A rise in diabetes was also seen in the United Kingdom in children 5 to 9 years in 1995 following a massive measles and rubella immunization program in that age group, according to Classen's data.
Classen's analysis of pertussis vaccine had similar results. He said that the incidence of diabetes in children younger than 5 years in Finland rose 64% after the pertussis vaccine was made more antigenic. His U.S. pertussis studies in Allegheny County, Pennsylvania, found that diabetes incidence rates decreased during the pertussis scare of 1975-1979 and rose again following the scare.
Hepatitis B immunization began in New Zealand in 1989, followed by an increase in diabetes incidence, according to Classen's data. Almost all the immunizations occurred in children 6 weeks or older.
Haemophilus influenzae type b (Hib) vaccine is another vaccine implicated by Classen's group in their reports. Because Hib vaccine is never given at birth, DeStefano said the CDC is observing whether an increase in diabetes occurs following its administration, as implicated in Classen's study.
According to the CDC report, Classen's study conducted in Finland using Hib vaccine involved more than 100,000 children who randomly received either four doses of vaccine starting at 3 months of age or a single dose at 24 months of age.
During a 10-year follow-up, 205 children in the multiple-dose group developed diabetes, compared with 185 in the single-dose group. The results of the study are inconclusive because the exact number of children in each group is unknown.
Additional studies of a possible link between vaccines and diabetes are currently underway through the National Institutes of Health (NIH) and the CDC.
The NIH is sponsoring an extensive review of the world's literature and on-going research on the subject. The NIH is also planning an international conference on infections (including immunizations) and diabetes.
DeStefano said the CDC is working with four health maintenance organizations for its study, which will use automated vaccination data as well as health care data and diabetes registries. Based on an initial analysis that looked at available computerized data sets, investigators determined that individual chart reviews were necessary to attain more details about vaccination information.
The issue first reached national prominence in January 1995 when the NIH convened a special meeting to review some of the data generated by Classen and to further explore the possibilities.
The consensus of the NIH panel was that no clear evidence existed to support a change in immunization policies or practices. The CDC agrees that the additional evidence since that time is not sufficient to change the NIH conclusion, DeStefano said.
For more information:
- Classen JB, Classen DC. Vaccines modulate type 1 diabetes. Diabetologia 1996;39:500-1.
- Classen DC, Classen JB. The timing of pediatric immunization and the risk of insulin-dependent diabetes mellitus. Infectious Diseases in Clinical Practice 1997;6:449-54
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