Surveillance for adverse events following immunization in Hebei Province, China, 2018-2020

The aim of this study was to analyze the incidence and characteristics of adverse events following immunization (AEFI) with post-licensure vaccines used in Hebei province from 2018 to 2020 and to evaluate the safety of vaccines. All information of AEFI was gained from national adverse event following immunization surveillance system (NAEFISS) in Hebei Province from 2018 to 2020. Descriptive epidemiology method was used to analyze the data about AEFI in Hebei province. Reporting rates of AEFI were calculated by sex, age, city, categories of AEFI, severity of AEFI, reaction categories, etc. A total of 35,999 AEFI were reported through NAEFISS, and the average annual rate was 47.64/100,000 doses. The reporting rates of common adverse reactions and rare adverse reactions were 46.37/100,000 doses and 1.05/100,000 doses. The male-to-female ratio was 1.26:1. Most of the AEFI were concentrated in the ≤1 year age group and were reported in the second quarter and third quarter. The majority of AEFI were reported to be recovered or improved, and about 62% of the AEFI occurred within 24 hours after vaccination. Vaccines associated with the highest reporting rate of AEFI were diphtheria, tetanus and acellular pertussis combined vaccine (DTaP, 170.45/100,000 doses). The reporting rate of allergic rash was found to be the highest in the adverse reactions (0.29/100,000 doses). The majority of AEFI cases were common adverse reactions, while serious rare adverse reactions caused by vaccines were extremely uncommon, and all vaccines used in Hebei Province were safe.