[Tuberculin reaction in 4.5 months babies and 7 years old children, vaccinated with BCG at bith]

ABSTRACT

Approximately one-third of the world's population is infected with Mycobacterium Tuberculosis [T.B], which is an indicator of high distribution of these bacteria in our environment. The only vaccine currently available against TB is the attenuated Mycobacterium bovis strain bacillus Calmette-Gu‚rin [BCG], which used regularly for many years to prevent the tuberculosis in Iran and many part of the world. The efficacy of this vaccine varies in different populations, and is a matter for discussion. On this basis, the present study has been set up to determine the level of tuberculin reaction in 4.5 month and in 7 years old children that receive BCG vaccine at birth time, in Golestan province. 2700, 4.5 month infant and 2400, 7 years old children in Golestan province were chosen by cluster sampling after the proper permission from the parents, public health centers and educational authorities were taken. The presences of the BCG scar were assessed, and 0.1ml of 5tu tuberculin were injected subcutaneously. The induration was measured 48-72 h after tuberculin injection. The results were determined as percent and compare with t test. In these study 2559 infants and 2193 child were taken part in the final evaluation. The BCG Scar were present in 97.9% of infants and 87.8% of 7 years children, this difference was meaningful. The average induration in 4.5 months babies were 2.29 mm, and in 7 years child was 0.66 mm, this difference was significant [P<0.05]. More than 44.7% of babies and 82% of 7 years children did not show any reaction after PPD test, this difference was also significant [P<0.05]. The level of positive tuberculin reaction in infants of this province in spite of vaccination was very low, and this level was reduced after 7 years time, this indicate that BCG vaccination at birth did not have any major role in positive tuberculin reaction. Our results also indicate that the presence of scar can be a good indicator for previous vaccination. In regard to the negative tuberculin reaction in majority of babies, it is suggested to evaluate the efficacy of BCG vaccine in preventing the TB disease itself, by other method such as studying the TB incidence among children in long term or by determination of cytokines level after tuberculin injection