No association between HPV vaccine and reported post-vaccination symptoms in Japanese young women: Results of the Nagoya study.

Nagoya City introduced free HPV vaccination in 2010 and in April 2013 the Ministry of Health, Labour and Welfare included the HPV vaccine in the National Immunization Program. However, in June 2013, the Ministry suspended proactive recommendation of the vaccine after unconfirmed reports of adverse events. To investigate any potential association between the vaccine and reported symptoms, Nagoya City conducted a questionnaire-based survey. Participants were 71,177 female residents of Nagoya City born between April 2, 1994 and April 1, 2001. The anonymous postal questionnaire investigated the onset of 24 symptoms (primary outcome), associated hospital visits, frequency, and influence on school attendance. Totally, 29,846 residents responded. No significant increase in occurrence of any of the 24 reported post-HPV vaccination symptoms was found. The vaccine was associated with increased age-adjusted odds of hospital visits for "abnormal amount of menstrual bleeding" (OR: 1.43, 95% CI: 1.13-1.82), "irregular menstruation" (OR: 1.29, 95% CI: 1.12-1.49), "severe headaches" (OR: 1.19, 95% CI: 1.02-1.39), and chronic, persisting "abnormal amount of menstrual bleeding" (OR 1.41, 95% CI: 1.11-1.79). No symptoms significantly influenced school attendance and no accumulation of symptoms was observed. The results suggest no causal association between the HPV vaccines and reported symptoms.