Two doses of quadrivalent HPV vaccine in teens noninferior to three in adults
The immunogenicity of two doses of the quadrivalent HPV vaccine in adolescents is comparable to that of three doses in adults up to 120 months after the last dose, according to a follow-up of a randomized control clinical trial.
According to Robine Donken, PhD, a postdoctoral research fellow at the Vaccine Evaluation Center at the University of British Columbia’s Children’s Hospital Research Institute, licensure of the HPV vaccine for adolescents focused on studies about the immunogenicity-bridging abilities of the vaccine rather than efficacy.
“The costs of the HPV vaccine are high, but it also has high efficacy and strong immunogenicity,” she told Infectious Diseases in Children. “There was a strong interest for alternative dose schedules.”
Donken and colleagues conducted a post hoc analysis of data from a 2013 trial where girls aged 9 to 13 years received either three doses of quadrivalent HPV vaccine at 0, 2 and 6 months or two doses at 0 and 6 months. The outcomes of these schedules were compared with those of women aged 16 to 26 years receiving the three-dose schedule at 0, 2 and 6 months. The researchers also compared the immunogenicity of two doses compared with three in the younger age group.
For the follow-up, the researchers tested antibody levels against HPV serotypes 6, 11, 16 and 18 using the competitive Luminex immunoassay (cLIA) and the total immunoglobulin G assay (TIgG). Donken and colleagues measured and compared geometric mean titers (GMTs) and seropositivity of teens after 60 months, and all received follow-up up to 120 months.
When the researchers examined seropositivity rates for all groups available at 120 months — 35 teens receiving two doses, 38 teens receiving three doses and 30 women receiving three doses — all were above 95% against all HPV vaccine serotypes, excluding HPV serotype 18. Women on the three-dose schedule had the lowest seropositivity against serotype 18 (60%; 95% CI, 40.6%-77.3%).
Donken and colleagues noted that GMT ratios for both the two- and three-dose adolescent schedule were noninferior to the three-dose adult schedule for vaccine serotypes when tested with cLIA. The researchers observed similar trends between cLIA and TIgG tests.
“These findings underline the validity of the current recommendations for vaccinating adolescents with a two-dose schedule,” Donken said. – by Katherine Bortz
Disclosures: Donken reports receiving grants from the Canadian Immunization Research Network and Michael Smith Foundation of Health Research outside the submitted work. Please see the study for all other authors’ relevant financial disclosures.