Post-Marketing Surveillance of Adverse Events Following Immunization with

Introduction: The Methods: We extracted data on Hib vaccine doses administered and adverse events following immunization (AEFI) reported between 2010 and 2021 from the Chinese National Immunization Information System (CNIIS). A descriptive analysis was conducted to examine the characteristics and incidence rates of AEFI with the Hib vaccine. Results: In China, between 2010 and 2021, a total of 52,910 AEFIs with the Hib vaccine were reported, resulting in an overall AEFI reporting rate of 38.10 per 100,000 doses. Common (typically minor) and rare (potentially serious) vaccine reactions occurred at rates of 34.71 and 2.78 per 100,000 doses, respectively. Among the common vaccine reactions, the incidences of fever (axillary temperature ≥38.6 ℃), injection site redness and swelling (>2.5 cm in diameter), and injection site induration (>2.5 cm in diameter) were 11.93, 9.69, and 3.38 per 100,000 doses, respectively. Rare vaccine reactions included anaphylactic rash, angioedema, and febrile convulsion with reported incidences of 2.42, 0.10, and 0.05 per 100,000 doses, respectively. The incidence of serious rare vaccine reactions was 0.16 per 100,000 doses. Conclusions: The reported incidence of AEFI with the Hib vaccine was low, with the occurrence of serious rare adverse reactions also being markedly low throughout the period 2010-2021 in China.