Abstract: Objective To analyze surveillance data on adverse events following immunization (AEFI) associated with the Bacillus Calmette-Guérin (BCG) vaccine in Hubei Province from 2017 to 2023, and to evaluate the vaccine's safety profile. Methods Data on the number of BCG vaccine doses administered and individual AEFI cases from 2017 to 2023 were retrospectively collected from the Chinese Center for Disease Control and Prevention Information System and the Hubei Provincial Immunization Program Information System. A descriptive analysis was conducted to characterize the reported incidence and epidemiological features of AEFIs. Results A total of 313 BCG-associated AEFI cases were reported in Hubei Province from 2017 to 2023, with an average annual reported incidence of 10.07 per 100 000 doses. The reported incidences of common and abnormal reactions were 3.64 and 6.02 per 100 000 doses, respectively. The incidence rates for serious and non-serious AEFIs were 1.58 and 8.50 per 100 000 doses, respectively. AEFI cases were reported in all months, with a peak period observed from May to August (44.73%). Cases were reported in all prefectures of the province except for Ezhou City, with average annual reported incidences ranging from 3.19 to 35.03 per 100 000. The male-to-female ratio of cases was 1.93∶1, with the majority (70.61%) occurring in infants aged six months or younger. The onset of common reactions was primarily concentrated at ≥91 days (26.61%) and<1 day (23.38%) post-vaccination. Abnormal reactions predominantly occurred ≥8 days post-vaccination (91.98%). More specifically, BCG-associated lymphadenitis was most commonly observed ≥31 days post-vaccination (91.09%), whereas local abscesses were most frequent ≥8 days post-vaccination (92.11%). Conclusion The reported incidence of BCG-related AEFIs in Hubei Province exhibited an initial increase followed by a subsequent decline. Serious adverse events are exceedingly rare, indicating a favorable safety profile for the vaccine. It is imperative to enhance training and guidance in AEFI surveillance to improve the quality of investigation and diagnosis. Furthermore, conducting evaluative monitoring, establishing standardized treatment protocols for the prompt identification and management of severe BCG-related AEFIs, and implementing measures to reduce the incidence of abnormal reactions are warranted.

Key words: Bacillus Calmette-Guérin (BCG) vaccine, Adverse events following immunization (AEFI), Vaccine safety, Surveillance data, Common reactions, Abnormal reactions