| Funding sources: None.
| Disclosures: Dr Kreuter has served as a speaker for Meda Pharma, for which he received honoraria. He also serves on a scientific advisory board of MSD Sanofi Pasteur. Dr Esser takes part as local principal investigator in the Human Papillomavirus Quadrivalent Vaccine Study program of Merck and MSD Sanofi Pasteur. Dr Wieland has no conflicts of interest to declare.