We evaluated the immunogenicity and safety of 2 tetravalent HPV vaccines.
Immune responses were compared to the licensed bivalent HPV-16/18 L1 VLP vaccine.
HPV-16 and -18 antibody titers were lower when additional HPV L1 VLPs were added.
Immune interference was not always overcome by changing the VLP dose or adjuvant.
All vaccine formulations had an acceptable reactogenicity and safety profile.