Objective To analyze the characteristics of suspected adverse events following immunization (AEFI) with human papillomavirus (HPV) vaccine administered in Ningbo city and evaluate the safety of the vaccine.

Methods Data on reported AEFI cases after HPV vaccination from 2018 to 2022 were collected from the National Adverse Event Following Immunization Surveillance System. The number of HPV vaccine doses administered was obtained from the Zhejiang Province Vaccine and Immunization Management Information System. Indicators such as the reported AEFI incidence rates, distribution characteristics, and clinical symptoms were analyzed to assess the safety of HPV vaccination.

Results A total of 843 913 doses of HPV vaccine were administered in Ningbo city over a 5-year period, during which 262 cases of AEFI related to HPV vaccination were reported. The mean annual reporting incidence rate was 31.05 per 100 000 doses. The reported AEFI cases were predominantly adverse reactions (259 cases), with a total reporting incidence rate of 30.69 per 100 000 doses. Among the adverse reactions, 253 cases (96.56%) were common reactions, and 6 cases (2.29%) were rare reactions, with incidence rates of 29.98 and 0.71 per 100 000 doses, respectively. The reporting incidence rates of main common reactions were 15.76, 9.01, and 8.06 per 100 000 doses for local redness and swelling, fever, and local induration, respectively. The reported rare reactions included 3 cases of allergic rash and 2 cases of urticaria. No serious AEFIs were reported. The reported AEFIs mainly occurred within 0 - 1 day after HPV vaccination (217 cases, 82.82%) and following the first dose (112 cases, 42.75%). They were primarily observed in the 20 - 39 age group (201 cases, 76.72%). All 262 AEFI cases recovered or improved during the follow-up observation periods.

Conclusions From 2018 to 2022 in Ningbo city, the reported AEFIs associated with the HPV vaccine were primarily common reactions, with very few rare reactions and no serious AEFIs reported, indicating a favorable safety profile for the HPV vaccine.