Adverse events following immunization with inactivated influenza vaccine in Hangzhou, 2019 – 2021: a surveillance data analysis

  Objective  To analyze the incidence and characteristics of adverse events following immunization (AEFIs) with vaccination of inactivated influenza vaccine (IIV) during 2019 – 2021 in Hangzhou city, Zhejiang province, China.

  Methods  Data about IIV vaccination and IIV AEFI was collected from the Zhejiang Information System for Immunization Program and the National AEFI Information System. A descriptive analysis on the reported incidence of IIV AEFI was conducted.

  Results  A total of 568 IIV AEFI cases were reported and the reported incidence rate (1/per 100 000 doses administered) was 40.48 during 2019 – 2021 in the city. The reported incidence rate (1/per 100 000 doses administered) was 34.70 (487 cases) and 3.42 (48 cases) for common and rare adverse reactions. The reported incidence rate were 88.71 (180 cases), 51.11 (162 cases), 38.87 (74 cases), and 21.93 (152 cases) for the vaccine recipients aged < 3, 3 – 17, 18 – 59, and ≥ 60 years, respectively. Compared to those among the recipients of trivalent IIV (IIV3), significantly higher incidence rate (1/per 100 000 doses administered) of local swelling (25.64 vs. 14.13) and induration (9.30 vs. 5.19) were reported among the recipients of tetravalent IIV (IIV4) (both P < 0.05). But no significant difference in overall incidence of AEFIs was observed between IIV3 and IIV4 (P > 0.05).

  Conclusion  The reported incidence of IIV AEFI was low during 2019 – 2021 in Hangzhou city, indicating a good safety of IIV3 and IIV4 vaccination.