The HPV-16/18 AS04-adjuvanted vaccine demonstrated efficacy and immunogenicity without any safety concerns, according to recent study results published in Human Vaccines and Immunotherapeutics.
The study was a follow-up of a double blind, randomized, placebo-controlled trial (HPV-001). Researchers assessed the efficacy of a bivalent HPV-16/18 vaccine (Cervarix, GlaxoSmithKline) in a subset of 437 women from the original study enrolled at five Brazilian centers. Participants were aged 15 to 25 years, and had previously been assigned vaccination or placebo. For the current study (HPV-023), researchers followed participants for more than 9 years, taking annual measurements of anti-HPV-16/18 antibodies.
The researchers assayed cervical samples every 6 months for HPV DNA and performed cyto-pathological examinations on a yearly basis. During the course of the study, no new HPV-16/18 infections or associated abnormalities were reported in the vaccine group.
Results indicated that vaccine efficacy against HPV-16/18 incident infection was 100% (95% CI, 66.1-100). During the 9.4 years of follow-up, vaccine efficacy was 95.6% (95% CI, 86.2-99.1) against incident infection, 100% (95% CI, 84.1-100) against 6-month persistent infection, and 100% (95% CI, 61.4-100) against 12-month persistent infection.
In terms of cyto-histopathological abnormalities, the vaccine yielded 97.1% (95% CI, 82.5-99.9) efficacy against atypical squamous cells of undetermined significance, 95% (95% CI, 68-99.9) efficacy against low-grade squamous intraepithelial lesions, 100% (95% CI, 45.2-100) efficacy against cervical intraepithelial neoplasia grade 1 and 100% (95% CI, -128.1-100) efficacy against cervical intraepithelial neoplasia grade 2 related to HPV-16/18.
Seropositivity of the vaccine to HPV-16/18 was ongoing, and antibodies were substantially above normal infection levels. IgG antibodies maintained continuous high volumes, leveling out roughly 18 months after the first vaccine dose and remaining stable.
No safety issues were reported with the vaccine.
According to Ronald Ellis, MD, editor-in-chief of Human Vaccines and Immunotherapeutics, these findings suggest that for teens and young adults at risk, the vaccine may have long-term value.
"HPV vaccine has been distinctive in having achieved 100% protective efficacy in licensure trials and showing excellent persistence of protective immunity,” Ellis said in a press release. “The data in this article show persistence of protection for about one decade, which should give adolescents and young adults an increased level of confidence in taking this vaccine and being protected against the development of cervical and other cancers."
Disclosure: The researchers report no relevant disclosures.