To further standardize the safety evaluation of clinical trials of preventive vaccines and accelerate the integration of adverse event classification standards with international standards, NMPA has organized the drafting of and released on December 31, 2019 the Guidelines for Adverse Event Classification Standards for Clinical Trials of Preventive Vaccines. The Guidelines for Adverse Reaction Classification Standards for Clinical Trials of Preventive Vaccines, issued by the former State Food and Drug Administration (SFDA Department of Drug Registration [2005] No. 493) in 2005, shall be repealed simultaneously.