Background: Most cervical cancers are caused by vaccine-preventable infections with human papillomaviruses (HPV). The HPV prophylactic vaccines Gardasil and Cervarix have been widely used for >10 years and are reported to induce high antibody levels. A head-to-head comparison of the antibody responses induced by the 2 vaccines has been performed only up to 5 years.
Methods: Among 3300 Finnish females aged 16-17 years who got 1 of the 2 HPV vaccines in phase 3 licensure trials, virtually all consented to registry-based long-term follow-up. Linkage with the Finnish Maternity Cohort found that they donated >2500 serum samples up to 12 years later. Sera of 337 (38.6%) Gardasil and 730 (30.3%) Cervarix vaccine recipients were retrieved from the Finnish Maternity Cohort biobank and type-specific anti-HPV antibody levels were determined using in-house multiplexed heparin-HPV pseudovirion Luminex assay.
Results: Anti-HPV-16 and anti-HPV-18 antibody levels remained stable and above natural infection-related antibody levels for up to 12 years for most vaccine recipients. The median antibody levels were higher among Cervarix recipients 7-12 years post vaccination (P < .0001).
Conclusions: The stability of vaccine-induced antibody levels is in accordance with the high long-term protection reported previously. The differences in antibody levels induced by the 2 vaccines imply that continued follow-up to identify possible breakthrough cases and estimation of the minimal protective levels of serum antibodies is a research priority.