BCG-Associated Complications Following Delayed Vaccination in Infants in Saudi Arabia: A Retrospective Cohort Study

Background: Bacillus Calmette-Guérin (BCG) vaccination is essential for preventing severe tuberculosis in early childhood. The BCG vaccine is administered at birth and carries a risk of disseminated disease, especially in immunocompromised infants. To reduce this risk, Saudi Arabia revised its national immunization policy in 2019, postponing BCG vaccination from birth until six months of age. Objectives: This study aimed to evaluate the incidence, clinical characteristics, and management of BCG-associated complications, specifically lymphadenitis, among infants receiving delayed vaccination. Methods: This retrospective cohort study was conducted at King Abdullah bin Abdulaziz University Hospital, Riyadh. Electronic medical records of infants vaccinated between 2019 and 2025 were reviewed. Results: Data from 994 infants were analyzed. The median age at vaccination was 28 weeks (IQR: 26-30). The overall incidence of BCG-associated complications was remarkably low at 0.5% (n = 5), comprising four cases of lymphadenitis (0.4%) and one case of BCGitis (0.1%). The median time to symptom onset was five weeks post-vaccination for lymphadenitis and 13 weeks for BCGitis. All complications were diagnosed clinically and presented with a mild clinical course. Management was 100% conservative, requiring no antibiotics, surgical intervention, or anti-tuberculosis therapy. All cases achieved complete resolution. Conclusions: Delaying BCG vaccination to six months of age significantly enhances safety, resulting in a substantially lower incidence of lymphadenitis compared to historical neonatal administration data. This strategy allows for greater immunological maturity and provides a critical screening window for primary immunodeficiencies, effectively minimizing vaccine-related morbidity while maintaining protective benefit.