Tuberculin Sensitivity Among Children Vaccinated with BCG Under Universal Immunization Programme V.K. Chadha, P.S. Jaganath and P. Kumar National Tuberculosis Institute, Bangalore, India Abstract. A tuberculin survey was conducted among 45988 children with BCG scar and 54227 children without BCG scar between 1-9 years of age and residing in selected rural areas of three defined zones of India. About 45-60% of the BCG- vaccinated children elicited reactions <5 mm in size and about 70-80% had reactions <10 mm. Therefore, in the majority of children (showing tuberculin reaction of <10 mm), BCG-induced tuberculin sensitivity does not interfere with interpretation of tuberculin test. The study also revealed that a proportion of reactions among BCG vaccinated children in 5-9 mm, 10-14 mm and 15-19 mm range may be attributable to BCG vaccination. Therefore, reactions between 10-14 mm and especially 15-19 mm among the vaccinated children must be interpreted carefully. However, 19 mm was observed as the upper limit for BCG induced tuberculin sensitivity and all reactions > 20 mm in size may be considered to be due to infection with tubercle bacilli, irrespective of the BCG vaccination status. [Indian J Pediatr 2004; 71 (12) : 1063-1068] E-mail : ntiindia @ blr.net.in, vin_chadha @ yahoo.com Key words: Tuberculosis; Infection; Tuberculin test; BCG vaccination BCG vaccination is known to induce a certain degree of tuberculin sensitivity, which might interfere with the interpretation of tuberculin test results. There is extensive literature on the patterns of tuberculin sensitivity among vaccinated children. In fact, this issue has been studied more than any other aspect of BCG. However, conflicting reports on tuberculin sensitivity patterns among BCG vaccinated children have emerged from these studies. 1-21 This variability has been attributed to various factors like age at vaccination, dose and type of vaccine, dose and type of tuberculin used, interval from vaccination to tuberculin testing and whether vaccine was given under controlled or program conditions. 1-7,~-2~ During the mass BCG campaigns during 1950s, BCG induced tuberculin sensitivity was observed to be pronounced and akin to the sensitivity induced by natural tuberculous infection 1. Similar observations were also made in India even though such sensitivity was found to be lower than that in some other countries) During BCG campaigns, implemented as vertical programs, the full dose of vaccine was given to everyone who elicited smaller reactions to the pre-vaccination tuberculin test. Vaccine induced sensitivity was assessed by tuberculin testing after few weeks of vaccination. During the BCG prevention trial at Chingleput, tuberculin sensitivity among 1-4-year-old children observed at 2.5 months after BCG vaccination was found to be similar to natural infection even with a weaker dose of the vaccine. 6.8 Correspondenceand Reprintrequests : Dr. V.K.Chadha, National Tuberculosis Institute, 8, BellaryRoad, Bangalore-560003, India. Fax"080-3440952 (*See commentary on page 1083o1084) Indian Journal of Pediatrics, Volume 71--December, 2004 However, the vaccine-induced sensitivity was found to have waned markedly at 2.5 years after vaccination. During this trial, trained personnel under meticulously implemented research conditions administered the vaccine. Meanwhile, there were changes in vaccination policy in India with the introduction of Expanded Program of Immunization (EPI) in 1970s and later Universal Immunization Program (UIP) in early 1980s. Under the current UIP policy, a reduced dose (0.05 ml after re- constitution) of BCG -Danish 1331 strain, is administered immediately after birth in case of institutional deliveries and latest by 4-6 weeks to other children by multi- purpose health workers, without prior selection by pre- vaccination tests. 22 Dick Menzies has recently summarized the evidence from a number of countries, on tuberculin reactivity after BCG vaccination in infancy and concluded that tuberculin reactivity after BCG vaccination in infancy wanes rapidly in most individuals. 21 However, the number of children studied was small in most of these except in one study conducted in Montreal. The information on tuberculin test data among children vaccinated under UIP of India has been rather limited. For that reason, a large amount of data now available from a recently concluded nation- wide tuberculin survey in India, was analyzed to compare tuberculin sensitivity patterns among children with and without BCG scar, and to study their trends with age. The results presented hereunder would be of immense value in interpretation of tuberculin test results among BCG vaccinated children. 1063