Updates on Vaccine Safety and Post-Licensure Surveillance for Adverse Events Following Immunization in South Korea, 2005-2017

Purpose: Vaccine hesitancy is among the top ten threats to global health, and access to precise data on adverse events following immunization (AEFIs) is imperative to alleviate public concerns surrounding vaccines. This study aimed to present the overall trends of AEFIs reported in South Korea. Materials and Methods: We evaluated the trends of AEFIs using the Korea Institute of Drug Safety & Risk Management-Korea Adverse Event Reporting System database between January 2005 and December 2017. AEFIs were classified into five categories to evaluate associations between vaccines and AEFIs through a case-non-case study: neurologic reactions, general systemic reactions, local reactions, allergic reactions, and others. Results: Among 54378 reported adverse events (AEs) associated with all vaccines approved in South Korea, more than half (56.7%) occurred following influenza vaccination, followed by the pneumococcal (11.6%) and Bacillus Calmette-Guerin (BCG) vaccines (5.0%). After immunization with most vaccines, general systemic reactions were most common, followed by local and neurologic reactions. Adjusted reporting odds ratios were calculated for all neurologic, general, local, and allergic reactions: of all vaccines, rotavirus [neurologic 2.43, 95% confidence interval (CI), 2.25-2.62], BCG (general; 2.20, 95% CI, 1.91-2.53), BCG (local; 3.15, 95% CI, 2.69-3.68), and Japanese encephalitis (allergic 2.38, 95% CI, 1.98-2.87) vaccines showed the highest values. Conclusion: The majority of reported AEFIs were non-serious and mostly general systemic reactions. Sufficient knowledge on the AEFIs would secure public confidence on the safety of vaccines, thereby reducing public health burden from vaccine-preventable diseases.