Data from an ongoing study indicate that the bivalent HPV vaccine induced high anti-HPV antibody levels up to 6 years after vaccination, which were predicted to remain above those induced by natural infection for at least 20 years.
Tino F. Schwarz, MD, of the Stiftung Juliusspital in Weurzburg, Germany, and colleagues enrolled girls aged 10 to 14 years who participated in a previous study during which they received three doses of bivalent HPV vaccine (Cervarix, GlaxoSmithKline), which protects against HPV serotypes 16 and 18.
Study participants had a mean age of 18 years when the open 3-year study began and were invited to continue follow-up for up to 10 years post-vaccination. Of the 625 girls invited, 529 completed month 72 follow-up. The study is ongoing.
At 72 months, all participants remained seropositive for anti-HPV-16 and HPV-18 antibodies. Geometric mean titers (GMTs) were 1,962 enzyme-linked immunosorbent assay (ELISA) units per mL for vaccine-induced anti-HPV-16 antibodies and 749.6 ELISA units per mL for anti-HPV-18 antibodies.
Anti-HPV-16 and 18 antibody GMTs were 65.8 and 33-fold higher than those induced by natural infection.
Piece-Wise and modified Power-Law models predicted mean anti-HPV-16 and 18 antibody levels would remain above those associated with natural infection for at least 20 years, according to Schwarz and colleagues. Due to variability of individual vaccine responses, additional model-based estimations were performed to predict duration and indicated that 95% of participants would have anti-HPV-16 and 18 antibody levels above those induced by natural infection. Predicted durations were 31 years and 22.7 years for anti-HPV-16 antibodies and anti-HPV-18 antibodies, respectively, among girls vaccinated at 10 to 14 years of age. These predicted durations were longer than those for girls vaccinated at 15 to 25 years of age.
None of the 110 severe adverse events reported among 74 participants were considered related to vaccination.
“This long-term follow-up study showed that the HPV-16/18 AS04-adjuvanted vaccine, when administered to preteen/adolescent girls, had a clinically acceptable safety profile, was immunogenic up to 6 years post-vaccination, and induced mean anti-HPV-16 and-18 antibody titers that were predicted to persist for at least 20 years above those associated with natural infection. These results support the introduction of the HPV-16/18 AS04-adjuvanted vaccine in immunization programs for young adolescent girls,” the researchers concluded.
Disclosure: The researchers have financial ties with GlaxoSmithKline, which provided funding for the study.