Long term immunogenicity of two doses of the quadrivalent HPV vaccine and the effect of an additional dose given five years post-primary vaccination.

BACKGROUND

Antibody persistence in girls (age 9-11 years) receiving two quadrivalent vaccine (4vHPV) doses and impact of an additional dose five years post-primary vaccination were assessed.

METHODS

Girls vaccinated with two 4vHPV (Gardasil) doses (n = 496) were randomized to one- (2 + 1) or no-additional-dose groups five years post-first dose. Geometric mean concentrations (GMCs) for HPV types 6/11/16/18 were measured using M9ELISA at 5, 7.5, and 10 years post-primary vaccination.

RESULTS

Antibodies to 4vHPV-targeted types persisted in all participants at each time point in both study arms. Compared to the 2-dose group that had stable antibody levels up to 10 years, GMCs were higher in the 2 + 1 group at 7.5 and 10 years post-primary vaccination (p < .0001).

CONCLUSIONS

Two doses of 4vHPV administered at ages 9-11 confers stable antibody levels up to 10 years post-vaccination that can be enhanced with an additional dose given several years later, suggesting the presence of immune memory.