evaluation of children with complication of bcg vaccination in north of iran

background: although the efficacy of bacillus calmette-guerin (bcg) vaccine in the prevention of tuberculosis has been noted consistently, the use of bcg vaccine is not without risk. in this study we aimed to evaluate immunologically, children with complication of bcg vaccination in north of iran.materials and methods: this case-control study began in 30 jan 2013 and was completed in 2 jul 2015. in case group 35 patients with moderate to severe complications of bcg vaccination for tuberculosis (tb), have been enrolled.thecontrol group included 35 patients with mild complication and patients had no complications due to bcg vaccine.  routine and specific tests for evaluation of immunological function were performed.results: out of total number of 35 patients in case group, 3(8.6%) patients had severe complication, also they diagnosed as bcg-osis; 32(91.42%) cases had moderate symptoms‎. in the control group 25 (71.4%) patients had mild complications and 10(28.57%) patients had no complications. the mean of il-23 level in the two groups had significant difference (p= 0.027). there was a significant relationship about interleukin and interferon deficiency among patients with severe complications.  patients with mild to moderate complications of bcg vaccine were not associated with immunodeficiency. patients with severe complications of bcg vaccine, were associated with mendelian susceptibility to mycobacterial disease (msmd) primary ‎immunodeficiency (pid).conclusion: severe complications of bcg vaccine could be due to msmd and it may be associated with immune ‎deficiency in il 12/23.‎ bcg vaccination must be deferring in newborns in families with a history of death following presumed bcg or early death or recurrent infection, until suitable screening immunological tests exclude the pid.