Introduction Bacille Calmette-Guerin (BCG) vaccination has shown
promising therapeutic effects for type 1 diabetes (T1D). According to
recent studies, immunometabolism modification and regulation of T
lymphocytes constitute the proposed mechanisms by which BCG vaccination
may delay T1D onset. Clinical trial evidence from Turkey supports that
two to three doses of the BCG vaccine in childhood, with the first dose
administered in the first year of life, may prevent T1D. In the same
study, one or zero vaccinations appeared to have no effect in T1D onset
prevention. In Greece, the BCG vaccine was administered in a single dose
at the age of 9 years in elementary school. BCG vaccination was not
performed on a mandatory basis, creating one BCG vaccinated and one
non-vaccinated population. The aim of our study was to investigate the
possible effect of a single dose of BCG vaccine, at the age of 9 years,
on the time of T1D onset, in a population of BCG vaccinated and
non-vaccinated patients with diagnosed T1D. Methods To test this
hypothesis, a survey through the Pan-Hellenic Federation of People with
Diabetes (PFPD) was performed. In this observational, retrospective
study, participating patients provided information regarding age,
gender, time of diagnosis, and BCG vaccination status. Patients
diagnosed with T1D before the age of 9 years were excluded from the
analysis. Results The final sample included 196 patients (73 male and
123 female) with a mean age of 42.2 +/- 14.3 years and a mean duration
of diabetes of 16.8 +/- 12.9 years. Mean age of T1D diagnosis in the BCG
vaccinated group was 24.0 +/- 19.0 years, while the mean age of T1D
diagnosis in the BCG non-vaccinated group was 21.5 +/- 14.3 years (p =
0.03). No interaction was found between gender and the age of diagnosis
for BCG vaccinated and unvaccinated patients (p = 0.86). Conclusion The
results of our study suggest that a single dose of BCG vaccine,
performed at the age of 9 years, may delay the onset of T1D by 2.5
years. Additional studies of children receiving multiple doses of BCG
should be conducted to possibly prove prolongation of the disease-free
interval