Correlation between levels of human papillomavirus (HPV)-16 and 18 antibodies in serum and cervicovaginal secretions in girls and women vaccinated with the HPV-16/18 AS04-adjuvanted vaccine

This pooled analysis of data from four Phase III clinical trials was undertaken to assess the correlation between levels of anti-human papillomavirus (HPV)-16/18 antibodies in serum and cervicovaginal secretions (CVS) in girls and women vaccinated with the HPV-16/18 AS04-adjuvanted vaccine. Serum and CVS samples were collected from a subset of women aged 10-65 years (N=350) at pre-specified time-points from 7 to 36 months post-vaccination. Anti-HPV-16/18 antibody levels in serum and CVS were measured by enzyme-linked immunosorbent assay. Pearson correlation coefficients between serum and CVS antibody levels, standardized for total immunoglobulin G, were calculated at each time-point in women with detectable antibodies in both serum and CVS. All subjects had seroconverted at Month 7 and remained seropositive through Month 36 for both antigens. Geometric mean titers of anti-HPV-16/18 antibodies in serum were substantially higher at all time-points than those in a control group of women who had cleared a natural HPV infection in another trial. In women with detectable antibodies in both serum and CVS, good correlation was seen between HPV-16/18 antibody levels at all time-points (Pearson correlation coefficient: 0.84-0.92 for HPV-16 and 0.90-0.91 for HPV-18). The strong correlation between levels of HPV-16/18 antibodies in serum and CVS up to 36 months post-vaccination in girls and women vaccinated with the HPV-16/18 AS04-adjuvanted vaccine supports transudation of serum antibodies as the mechanism by which antibodies are introduced into CVS. These CVS antibodies may play a role in the protective efficacy of this vaccine.