NEW YORK (Reuters) -- The timing of immunizations in childhood can affect a child's risk of developing juvenile onset insulin-dependent diabetes (IDDM), according to a new report.
In the study, researchers identified a 33% drop in the incidence of type-I diabetes cases in children under age 15 in European countries where an anti-tuberculosis vaccine (BCG) was given at birth compared with countries where it was given after two months of age.
But a study of immunization practices in western Europe, New Zealand, and Iceland also linked an increase in the risk of developing type-I diabetes to administration of the BCG vaccine and the vaccine against hemophilus influenza B after the age of 8 weeks.
Study co-author Dr. David C. Classen, an epidemiologist and infectious diseases specialist at the University of Utah School of Medicine in Salt Lake City, says the findings require further study for verification. But he says they suggest that vaccines given at birth may prevent children from being colonized with diabetes-inducing coxsackie B viruses from their mothers.
But vaccination later in life may cause the release of these same viruses "that have chronically infected the host," write the researchers.
According to a report in the journal Infectious Diseases in Clinical Practice, the coxsackie B viruses may play a role in causing 27% or more cases of IDDM. The study team propose that a variety of vaccines given at birth may change the risk of type-I diabetes through their effect on the mediators of immunity in the newborn's system.
"The immune modulatory actions of vaccines have received little attention; however, the vaccine-induced interferon release may have a significant biologic effect on the incidence of diabetes," the researchers state.
According to Classen, after children are eight weeks or older, underlying infection and inflammation of insulin-secreting cells in the pancreas may be worsened by vaccination, thus increasing the risk of type-I diabetes.
Classen notes that the findings in favor of giving pediatric vaccines at birth are supported by animal studies. He cites research showing prevention of type-I diabetes in rodents given diphtheria-tetanus-pertussis-(DTP) vaccine and an increased rate of the disease in animals vaccinated after two months of age.
Still, the report notes other factors besides the timing of pediatric vaccines that may be responsible for the changes in the rates of type-I diabetes found in the study. These may include social factors such as income, population density and hygiene; natural infections with coxsackievirus B and other possible diabetes-inducing viruses; and genetic predisposition to type-I diabetes.
"Based on our epidemiological data and previous animal studies, there appears to be a very tight window in which conditions are ideal to administer the first dose of common vaccinations," Classen says. "The next step is to verify this hypothesis with a large clinical trial involving humans, either in the United States or abroad."
SOURCE: Infectious Diseases in Clinical Practice (1997;6)
