(P-367) The Patterns of Spontaneous Reports of Neurologic, Hematologic, and Immunologic Adverse Events Following Immunization in Korea

Background: Rare but serious neurologic, hematologic and immunologic adverse events (AEs) may occur following immunization. In particular, information on patterns of those AEs in vaccines would be helpful for surveillance of AEs of special interest for COVID-19.

Objectives: We aimed to describe the patterns of spontaneous reports of neurologic, hematologic, immunologic AEs following immunization.

Methods: We used Korea adverse event reporting system database (KIDS-KD) between January 2011 and December 2019. Based on literature review, we included generalised convulsive seizures, Guillain–Barré syndrome, acute disseminated encephalomyelitis (ADEM), aseptic meningitis, encephalitis, and myelitis as neurologic AEs. In addition, we included thrombocytopenia as hematologic AE, and included anaphylaxis and vasculitis as immunologic AEs. We defined study AEs using World Health Organization Adverse Reaction Terminology (WHO-ART). We analyzed annual number of reports and characteristics including age groups and vaccines associated with each AE.

Results: A total of 39,195 spontaneous reports on vaccines with 129,708 vaccine-AEs pairs were identified between 2011 and 2019 in Korea. The total number of reports of neurologic, hematologic and immunologic AEs were 549 (median 63/ year (interquartile range (IQR) 18-74), 77 (median 5.5/ year, IQR 0-15), 182 (median 16.5/ year, IQR 6-25), respectively. The number of total reports were 122 reports for Guillain–Barré syndrome and 182 reports for anaphylaxis. The both Guillain–Barré syndrome (49 reports, 40.2%), anaphylaxis (50 reports, 27.5%) were reported most frequently in 16 to 64 years age group. The frequent vaccine of Guillain–Barré syndrome, anaphylaxis were influenza (97 reports, proportion: 0.27%) and Japanese encephalitis vaccine (16 reports, 0.59%), respectively.

Conclusions: Although potential problem of under-reporting should be considered, the information on baseline patterns of spontaneous reports for neurologic, hematologic, immunologic events following immunization would be useful for future vaccine safety surveillance.