Antibody responses among adolescent females receiving two or three quadrivalent human papillomavirus vaccine doses at standard and prolonged intervals

Abstract

Background: The originally recommended dosing schedule, 0, 2, 6 months, for the 3-dose quadrivalent human papillomavirus vaccine (4vHPV) was often not followed, resulting in longer than recommended intervals between doses and interest in the effect of prolonged intervals. Recent two-dose recommendations require investigations into the effect of delaying dose 2.

Methods: This multi-site, prospective study enrolled healthy 9-17 year old girls (n = 1321) on the day of or within 28 days following a third dose of 4vHPV vaccination. Antibody titers to 4vHPV types were measured at one and six months post-dose 3 from all participants and post-dose 2 from participants who were on time for dose 3. To compare antibody responses, participants were categorized into groups: second and third doses on time (control group); on-time dose 2, substantially late dose 3 (group 2); substantially late dose 2, on-time dose 3 (group 3); both doses substantially late (group 4). Analyses compared age-adjusted geometric mean titers (GMTs) at one-month and six-months post-dose 3, effect of delaying the second dose, and two versus three doses as well as post-dose 2 GMTs, stratified by age.

Results: Compared to on-time dosing, one-month post-dose 3 GMTs were non-inferior in groups 2, 3, and 4 and were superior in group 2. Six month post-dose 3 GMTs were superior in groups 2, 3, and 4 for each genotype, except HPV 18 in group 3. Age-adjusted post does 2 titers were significantly lower than post-dose 3 titers when dose 2 was on time but were significantly higher when dose 2 was substantially late. Participants ≥15 years old had no difference in post-dose 2 titers compared to <15 year olds when dose 2 was substantially delayed.

Conclusions: Prolonged intervals between doses do not appear to diminish and may enhance antibody response to 4vHPV. ClinicalTrials.gov (NCT00524745).

Keywords: Dosing; Geometric mean titers; Human papillomavirus; Immunity; Interval; Vaccine.

Figure 1. Number of participants with immunogenicity results

Abbreviations: OT/OT, both doses on time; OT/SL, dose 2 on time/dose 3 substantially late; SL/OT, dose 2 substantially late/dose 3 on time; SL/SL, both doses substantially late; LTF, lost to follow-up; NC, noncompliance; WP, withdrawn by parent; WI, withdrawn by investigator; NV, enrolled but not vaccinated. ¹ Participants were enrolled either before or after HPV vaccine dose 3 ² Participants in Group 1 and Group 3 who enrolled before receiving HPV vaccine dose 3 had a pre-dose 3 blood draw ³ Data has been combined for simplicity as no significant differences were detected between groups for any period ⁴ The number of participants at each analysis point does not add up to the total participant numbers in the group because not all participants were available at all visits. Some participants had data from the 1 month post dose 3 but not the 6 month post dose 3 visit; other participants had data from the 6 month post dose 3 visit but not the 1 month post dose visit.