Safety concerns with human papilloma virus immunization in Japan: Analysis and evaluation of Nagoya City's surveillance data for adverse events

AIM: To assess the safety of human papilloma virus (HPV) vaccines by using data from the “Nagoya City Cervical Cancer Immunization Program Survey”. METHODS: Unadjusted odds ratios (OR) were calculated between HPV‐vaccinated cases and un‐vaccinated controls. Age‐stratified analyses were performed to evaluate the interaction between age and events. Adjusted ORs were also estimated with multiple logistic regression models. RESULTS: In the 15–16‐year‐old group, the unadjusted ORs were significantly higher for symptoms of memory impairment, dyscalculia, and involuntary movement. The age‐adjusted multivariate analyses demonstrated that the vaccinated cases were less likely than the unvaccinated controls to have experienced symptoms in almost all symptoms, except for two symptoms such as involuntary movement and weakness. However, study period‐adjusted multivariate analyses demonstrated that the vaccinated cases were significantly more likely than un‐vaccinated controls to have experienced symptoms of memory impairment and involuntary movement. CONCLUSIONS: Based on our analysis using data from the Nagoya City surveillance survey, a possible association between HPV vaccination and distinct symptoms such as cognitive impairment or movement disorders exists. A consistent causal relationship between HPV vaccination and these symptoms remains uncertain. However, given the seriousness of symptoms, we believe that a more comprehensive and large‐scale study is essential to confirm the safety of HPV vaccination.