Table 2.

Predicted duration (after the first vaccine dose) over which 95% of women will maintain antibody titers above natural infection titers for: (A) serum anti-HPV neutralizing antibody response (assessed by PBNA) and (B) serum anti-HPV type-specific antibody response (assessed by ELISA), by piece-wise and modified power-law models (total vaccinated cohort, 3 doses)

(A) Serum neutralizing antibody responses (by PBNA analysis)
	Piece-wise model		Modified power-law model
Antigen†	HPV-16/18 vaccine	HPV-6/11/16/18 vaccine	HPV-16/18 vaccine	HPV-6/11/16/18 vaccine
	Predicted duration*		Predicted duration*
HPV-16
18-26 y	68.2 Y	1.7 Y	∞	1.8 Y
27-35 y	57.3 Y	1.3 Y	∞	1.1 Y
36-45 y	31.0 Y	1.3 Y	∞	1.2 Y
HPV-18
18-26 y	40.6 Y	9 M	∞	9 M
27-35 y	9.5 Y	< 7 M	∞	7 M
36-45 y	1.9 Y	7 M	1.8 Y	8 M
(B) Serum anti-HPV type-specific antibody responses (by ELISA analysis)
Antigen††
HPV-16
18-26 y	21.0 Y	11.3 Y	∞	∞
27-35 y	16.3 Y	8.4 Y	∞	∞
36-45 y	13.3 Y	9.3 Y	∞	∞
HPV-18
18-26 y	17.0 Y	1.4 Y	∞	1.3 Y
27-35 y	14.9 Y	1.1 Y	∞	1.1 Y
36-45 y	9.7 Y	1.3 Y	∞	1.3 Y

∞, infinity; ELISA, enzyme-linked immunosorbent assay; M, month; PBNA, pseudovirion-based neutralization assay; Y, year.

*Predicted time after the first dose ensuring that 95% of women will still have levels above natural infection levels.

† Natural infection levels (ED₅₀) for anti-HPV-16 and -18 neutralizing antibodies were 180.1 and 137.3, respectively.² Anti-HPV-16 and -18 nAb levels as measured by PBNA after natural infection within this study population (total vaccinated cohort) were determined in women of all age strata combined who were seropositive and cervical HPV-DNA negative for the type analyzed at baseline.

†† Natural infection levels (ELISA units/mL) for anti-HPV-16 and -18 antibodies were 29.8 and 22.6, respectively.⁹ Natural infection Immunoglobulin G geometric mean titers (GMT) correspond to the GMT of ‘cleared’ natural infection (i.e., subjects DNA-negative and seropositive at the time of enrolment), obtained from the Phase III study (HPV-008), as benchmarks.