Duration of protection is an important parameter in the assessment of HPV vaccines. Vaccines that induce long term protection are generally characterized by the generation of immune memory. The pivotal efficacy study of the 9vHPV vaccine has shown high efficacy to prevent infection and disease due to the vaccine HPV types through at least 5 years. The purpose of this study is to assess the potential of the 9vHPV vaccine to induce HPV type specific immune memory.
This is an open-label extension of the pivotal efficacy study of 9vHPV vaccine (Protocol V503-001). A subset of subjects (N=150) initially randomized to 9vHPV vaccine and who received 3 dose regimen of 9VHPV vaccine in the base study were enrolled in the study extension and administered a 4th dose of 9vHPV vaccine at Month 60. HPV type specific serum antibody levels were measured pre-dose 4 and at 7 and 28 days post dose 4. Serum anti HPV types 6, 11, 16, 18, 31, 33, 45, 52 and 58 antibody levels were assessed by competitive Luminex immunoassay (cLIA).
Pre-dose 4 geometric mean titers (GMTs) were lower than GMTs at Month 7 (4 weeks post dose 3) for all 9 vaccine HPV types. Administration of a fourth dose resulted in a rapid increase of GMTs for all 9 HPV types. GMTs at 7 and 28 days post dose 4 were higher than GMTs at 4 weeks post dose 3 for all 9 HPV types.
A three-dose regimen of the 9vHPV vaccine induces high efficacy and stable anti-HPV antibody levels for at least 5 years. Also, similar to what was previously observed with the quadrivalent HPV vaccine, administration of the 9vHPV vaccine induces robust immune memory. These findings suggest that the efficacy of the 9vHPV vaccine will be long lasting.