OBJECTIVE: To describe the complications and risks associated with BCG (Bacillus Calmette-Guérin) vaccination in patients diagnosed with SCID (Severe Combined Immunodeficiency). METHODS: This is a descriptive case series study. Medical charts were retrospectively reviewed for demographics, clinical manifestation, laboratory findings at diagnosis, outcome, and diagnosis of BCG vaccine-associated complications. RESULTS: Eleven patients diagnosed with SCID were enrolled. Ten were male. Seven (64 %) were considered probable SCID, while four (36 %) were considered definite SCID (genetically confirmed). The median age at the onset of symptoms was one month
the median age at SCID diagnosis was four months. Respiratory symptoms were the most frequent. Eight patients were vaccinated within seven days of life. Seven (87 %) of these patients experienced BCG vaccine-associated complications (86 % disseminated reactions
14 % localized reactions). BCG vaccine-associated complications were the first clinical manifestation in 75 % of the vaccinated patients. Less than half of the patients (36 %) underwent hematopoietic stem cell transplantation. The overall death rate was elevated (73 %)
the death rate related to BCG vaccination was 25 %. CONCLUSIONS: Patients with SCID can present a high rate of BCG vaccine-associated complications, which negatively impact the clinical outcome and mortality. Pediatricians must be aware that BCG vaccine-associated complications can be the first presentation and a warning sign of SCID. Implementing newborn screening for SCID in Brazil may represent a worthy opportunity to impact the health outcomes of affected infants significantly.