Hospital contacts and diagnoses five years prior to HPV vaccination among females referred for suspected adverse vaccine effects: A Danish nationwide case-control study.

Pre-vaccination morbidity and health care utilization seem to play a role in the path leading to suspected AE's after HPV vaccination. Since many of the diagnoses that were particularly increased before vaccination in referred females are overlapping with the most frequent symptoms reported, we cannot exclude that for some of the females, the suspected AE's might have been existing already before the vaccination.