Evidence of immune memory 8.5 years following administration of a prophylactic human papillomavirus type 16 vaccine

Abstract

Background: The duration of protection conferred by prophylactic human papillomavirus (HPV) L1 virus-like particle vaccines is a critical determinant of their public health impact. A feature of vaccines that confer long-term immunity is their ability to induce immune memory.

Objectives: We evaluated antibody responses against HPV types 6, 11, 16 and 18 following administration of the quadrivalent HPV-6/11/16/18 vaccine to women who had previously received a monovalent HPV-16 vaccine.

Study design: As part of an extended follow-up study conducted between 2006 and 2009 in Seattle, Washington, we administered the quadrivalent HPV-6/11/16/18 vaccine to 52 women (19 vaccine and 33 placebo recipients) who had participated in a monovalent HPV-16 vaccine trial 8.5 years earlier. Serum samples were tested for anti-HPV antibodies using competitive Luminex immunoassay.

Results: Following administration of the first dose of the quadrivalent HPV-6/11/16/18 vaccine, the anti-HPV-16 geometric mean titer among monovalent HPV-16 vaccine recipients (GMT=5024.0 milli-Merck units per milliliter [mMU/mL]; 95% confidence interval [CI]: 2710.1, 9313.6 mMU/mL) substantially exceeded that among the placebo recipients (GMT=136.1; 95% CI: 78.5, 235.8 mMU/mL; p<0.01) and their own highest anti-HPV-16 response observed during the original trial (GMT at month 7 of the original trial=1552.7 mMU/mL; 95% CI: 1072.6, 2247.7 mMU/mL; p<0.01).

Conclusions: The findings suggest that the administration of the three-dose regimen of the monovalent HPV-16 vaccine had produced memory lymphocytes, characterized by a heightened immune response following administration of the quadrivalent HPV-6/11/16/18 vaccine that effectively served as an antigen challenge.

Conflict of interest statement

Conflict of interest

The University of Washington has received funding from Merck & Co., Inc. to support HPV vaccine studies conducted by L.A.K. F.B.A. and J.T.B. were employees of Merck & Co., Inc. at the time of the conduct of the study.

Copyright © 2011 Elsevier B.V. All rights reserved.

Figures

Figure 1

Flow chart of the study population

Figure 2

Antibody responses against HPV type 6, 11, 16, and 18 following administration of the quadrivalent HPV-6/11/16/18 vaccine to women who had participated in the monovalent HPV-16 vaccine trial. The pre-dose 1 visit refers to the last visit before administration of the first dose of the quadrivalent vaccine or the visit during which the first dose of this vaccine was administered before blood draw, whichever came last. The post-dose 1 visit refers to the visit following administration of the first and before administration of the second dose of the quadrivalent vaccine.