Krogsgaard LW, Petersen I, Plana-Ripoll O, et al. - An infection in temporal proximity to HPV vaccination might be a trigger of the suspected adverse effects following HPV vaccination in a subset of females referred to an HPV center.

• In 2015, a human papilloma virus (HPV) vaccination crisis occurred in Denmark, with an increase in reports of suspected adverse effects after HPV vaccination and a dramatic decrease in the HPV vaccination uptake.

• As per available evidence, the HPV vaccine is identified as safe; the specific cause of the reported adverse effects is investigated.

• Given the overlapping of the reported symptoms with those characterized as chronic fatigue syndrome (CFS), these symptoms have been described as CFS-like.

• To a specialized hospital setting (HPV center), more frequently females who had a treated infection in temporal proximity to HPV vaccination, were referred for suspected adverse effects after HPV vaccination relative to HPV-vaccinated females without an infection.

• This finding was supported by the case-crossover and case time-control analyses made to control for potential unmeasured confounding.