Comparative immunogenicity and safety of human papillomavirus (HPV)-16/18 vaccine and HPV-6/11/16/18 vaccine: follow-up from months 12-24 in a Phase III randomized study of healthy women aged 18-45 years

Abstract

In this observer-blind study (NCT00423046), women (N=1,106), stratified by age (18-26, 27-35, 36-45 y), were randomized (1:1) to receive the HPV-16/18 vaccine (Cervarix®, GlaxoSmithKline Biologicals, Months 0, 1, 6) or the HPV-6/11/16/18 vaccine (Gardasil® Merck & Co., Inc., Months 0, 2, 6). Month 7 results were previously reported; we now report Month 24 results. In the according-to-protocol cohort for immunogenicity (seronegative and DNA-negative at baseline for HPV type analyzed), seropositivity rates of neutralizing antibodies (nAbs) [pseudovirion-based neutralization assay] were, across all age strata, 100% (HPV-16/18 vaccine) and 97.5-100% (HPV-6/11/16/18 vaccine) for HPV-16, and 99.0-100% (HPV-16/18 vaccine) and 72.3-84.4% (HPV-6/11/16/18 vaccine) for HPV-18. Corresponding geometric mean titers (GMTs) were 2.4-5.8-fold higher for HPV-16 and 7.7-9.4-fold higher for HPV-18 with the HPV-16/18 vaccine versus the HPV-6/11/16/18 vaccine; HPV-16 and HPV-18 GMTs were significantly higher with the HPV-16/18 vaccine than the HPV-6/11/16/18 vaccine (p< 0.0001) in the total vaccinated cohort (received ≥1 vaccine dose, irrespective of baseline sero/DNA-status). Similar results were obtained using enzyme-linked immunosorbent assay (ELISA). Positivity rates and GMTs of antigen-specific IgG antibodies in cervicovaginal secretions (ELISA) were not significantly different between vaccines. At Month 24, CD4⁺ T-cell responses for HPV-16 and HPV-18 were higher with the HPV-16/18 vaccine; memory B-cell response was higher for HPV-18 with the HPV-16/18 vaccine and similar between vaccines for HPV-16. Both vaccines were generally well tolerated. Although an immunological correlate of protection has not been defined, differences in the magnitude of immune response between vaccines may represent determinants of duration of protection.

Figures

Figure 1

Subject disposition. ATP, according to protocol. *Women may have been excluded for more than one reason, but were only counted for the primary reason for exclusion. Primary and secondary between-group comparisons to assess non-inferiority were performed in the according-to-protocol (ATP) cohort for immunogenicity on women who were seronegative and DNA-negative (by PCR) prior to vaccination for the antigen under analysis. Exploratory analyses of superiority and analyses of reactogenicity/safety were performed in the total vaccinated cohort on all women irrespective of their serostatus and DNA status prior to vaccination.

Figure 2

Geometric mean titers (GMTs), GMT ratios (GMR) and seropositivity rates for anti-HPV-16 and anti-HPV-18 serum neutralizing antibodies measured by pseudovirion-based neutralization assay at Months 6, 7, 12, 18 and 24 (ATP cohort for immunogenicity, seronegative and DNA-negative prior to vaccination). Solid black lines, Human Papillomavirus Bivalent (Types 16 and 18) Vaccine (Recombinant, adjuvanted, adsorbed) (Cervarix®); solid gray lines, Human Papillomavirus Quadrivalent (Types 6, 11, 16 and 18) Vaccine, Recombinant (Gardasil®). Error bars denote 95% confidence intervals (CIs) of GMTs. Dotted line, neutralizing antibody GMTs measured by PBNA in women in the total vaccinated cohort of the HPV-010 study who had cleared natural infection (prior to vaccination) [i.e., those who were seropositive and DNA-negative at Month 0]: 180.1 ED50 for HPV-16 and 137.3 ED50 for HPV-18. Dashed line, PBNA limit of detection (40 ED50). ED50, effective dose producing 50% response; GMR, geometric mean titer ratio; GMT, geometric mean titer. GMR = HPV-16/18 vaccine GMT divided by HPV-6/11/16/18 vaccine GMT at Month 7, 12, 18 or 24 computed using an ANOVA model on the log10 transformation of the titers in each age cohort. 95% CIs for GMRs are presented in parentheses. Seropositivity defined as neutralizing antibody titer ≥40 ED50. The ATP cohort for immunogenicity included all evaluable subjects who received three vaccine doses (i.e., those meeting all eligibility criteria and complying with the procedures defined in the protocol) for whom data concerning immunogenicity endpoint measures were available. This included subjects for whom assay results were available for antibodies against at least one study vaccine antigen (HPV-16 or HPV-18) at the timepoint under analysis.

Figure 3

Geometric mean titers (GMTs), Month 24 GMT ratios (GMR) and seropositivity rates for anti-HPV-16 and anti-HPV-18 IgG antibodies measured by enzyme-linked immunosorbent assay at Months 6, 7, 12, 18 and 24 (ATP cohort for immunogenicity, seronegative and DNA negative prior to vaccination). Solid black lines, Human Papillomavirus Bivalent (Types 16 and 18) Vaccine (Recombinant adjuvanted, adsorbed) [Cervarix®]; solid gray lines, Human Papillomavirus Quadrivalent (Types 6, 11, 16 and 18) Vaccine, Recombinant [Gardasil®]. Error bars denote 95% confidence intervals (CIs) of GMTs. Dotted line, GMTs for natural infection antibody levels (measured by ELISA) in the HPV-008 study: 29.8 ELISA units/mL for HPV-16 and 22.6 ELISA units/mL for HPV-18. GMTs for natural infection antibody levels (measured by ELISA) in the HPV-001 were 50 EU/mL for anti HPV-16 antibodies and 41 EU/mL anti HPV-18 antibodies. Vaccine induced antibody levels remained above the levels associated with natural infection in women in the ATP cohort for immunogenicity who received all three doses of HPV-16/18 vaccine through to 7.3 y follow-up of Study HPV-001 (HPV-007, HPV-023) ,, and through to Month 36 follow-up of Study HPV-008., Dashed line, ELISA limit of detection (8 ELISA units/mL for HPV-16 and 7 ELISA units/mL for HPV-18). Black square brackets, GMRs = HPV-16/18 vaccine GMT divided by HPV-6/11/16/18 vaccine GMT at Month 24 computed using an ANOVA model on the log10 transformation of the titers in each age cohort. Seropositivity defined as neutralizing antibody titer ≥8 ELISA units/mL for HPV-16 and ≥7 ELISA units for HPV-18. The ATP cohort for immunogenicity included all evaluable subjects who received three vaccine doses (i.e., those meeting all eligibility criteria and complying with the procedures defined in the protocol) for whom data concerning immunogenicity endpoint measures were available. This included subjects for whom assay results were available for antibodies against at least one study vaccine antigen (HPV-16 or HPV-18) at the timepoint under analysis.

Figure 4

Correlation between serum and cervicovaginal secretions for (A) HPV-16 and (B) HPV-18 IgG antibodies (standardized for total IgG antibodies) measured by enzyme-linked immunosorbent assay at Month 24 (ATP cohort for immunogenicity). CVS, cervicovaginal secretions; IgG, immunoglobulin G; R, Pearson correlation coefficient. Solid black lines and filled black circles, Human Papillomavirus Bivalent (Types 16 and 18) Vaccine (Recombinant, adjuvanted, adsorbed) [Cervarix®]; solid gray lines and filled gray circles, Human Papillomavirus Quadrivalent (Types 6, 11, 16 and 18) Vaccine, Recombinant [Gardasil®]. Only samples that tested positive for the antigen under analysis in both serum and CVS (i.e., double-positive samples) were analyzed. Vertical and horizontal lines represent the geometric means of the ratios between HPV-specific antibody titers and total IgG antibody content in serum and CVS samples, respectively. HPV-16/18-specific IgG levels were measured by VLP-specific ELISA. The total IgG antibody concentration of each sample was measured using an ELISA developed and validated in-house by GSK.

Figure 5

Proportion of responders for (A) HPV-16- and (B) HPV-18-specific B-cell responses at Months 7, 12, 18 and 24 (ATP cohort for immunogenicity; seronegative, DNA-negative and with no detectable HPV type-specific B-cells prior to vaccination). *p Cervarix®); white bars, Human Papillomavirus Quadrivalent (Types 6, 11, 16 and 18) Vaccine, Recombinant (Gardasil®). Responders defined as subjects with detectable HPV type-specific memory B-cells [>1 cell/million cells]. p-values were calculated using Fisher's exact test to compare proportion of responders.

Figure 6

Geometric means (GM) and GM ratios in responders only for (A) HPV-16- and (B) HPV-18-specific B-cells at Months 7, 12, 18 and 24 (ATP cohort for immunogenicity; seronegative, DNA negative and with no detectable HPV type-specific B-cells prior to vaccination). *p 1 cell/million cells)]. Solid black lines, Human Papillomavirus Bivalent (Types 16 and 18) Vaccine (Recombinant, adjuvanted, adsorbed) (Cervarix®); solid gray lines, Human Papillomavirus Quadrivalent (Types 6, 11, 16 and 18) Vaccine, Recombinant (Gardasil®). Error bars denote 95% confidence intervals of geometric means. Statistical comparison (GMR ANOVA p-value) was performed on B-cell responders only because data for all subjects in the subset did not follow a normal distribution.

Figure 7

Proportion of responders for (A) HPV-16- and (B) HPV-18-specific CD4+ T-cell response at Months 7, 12, 18 and 24 (ATP cohort for immunogenicity; seronegative, DNA-negative and with a HPV type-specific CD4+ T-cell response below 500 cells per million cells prior to vaccination). *p Cervarix®); white bars, Human Papillomavirus Quadrivalent (Types 6, 11, 16 and 18) Vaccine, Recombinant (Gardasil®). Responders defined as subjects with ≥500 HPV type-specific memory CD4+ T-cells expressing at least two of four immune markers [(CD40L, IL-2, TNFα, IFNγ)/million cells]. p-values were calculated using Fisher's exact test to compare proportion of responders.

Figure 8

Geometric means (GM) and GM ratios for (A) HPV-16- and (B) HPV-18-specific CD4+ T-cell response at Months 7, 12, 18 and 24 (ATP cohort for immunogenicity; seronegative, DNA-negative and with a HPV type-specific CD4+ T-cell response below 500 cells per million cells prior to vaccination). *p Cervarix®); solid gray lines, Human Papillomavirus Quadrivalent (Types 6, 11, 16 and 18) Vaccine, Recombinant (Gardasil®). Error bars denote 95% confidence intervals of geometric means. Statistical comparison (GMR ANOVA p-value) was performed on all subjects.