Background: The bacille Calmette-Guérin (BCG) vaccine is a widely practiced vaccine, which is useful for prophylaxis against tuberculosis. Disseminated BCG infection (BCG-osis) is one of the most important complications of this vaccine and can be seen in patients with an underlying immunodeficiency. This study was performed to determine the underlying defects in patients with BCG-osis.
Methods: Immunological evaluation was performed in all children who developed BCG-osis after vaccination in Tabriz, Iran.
Results: BCG-osis was documented in eight patients following vaccination. Axillary adenitis was detected in seven patients, and hepatosplenomegaly was also found in seven patients. Immunological studies revealed low serum IgG, IgM and IgA levels in all patients. Further investigations for enumeration of the lymphocyte sub-population revealed severe combined immunodeficiency (SCID) in all the patients. Three patients had T-B+NK- SCID, four had T-B-NK+ SCID, and one had T-B+NK+ SCID. Unfortunately, all the patients died due to the severe disseminated BCG infection.
Conclusions: Inoculation of live vaccines such as BCG should be postponed for a few months in suspected cases of primary immunodeficiency disease, until appropriate screening tests exclude this diagnosis; vaccination should then be performed in those with an intact immune system.