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HPV vaccine tolerated across three dosing schedules in Vietnam
Neuzil KM. JAMA. 2011;305:1424-1431.
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The quadrivalent human papillomavirus vaccine was immunogenic and well tolerated on alternative dosing schedules and comparable with the safety profiles of standard vaccine schedules among adolescent girls in Vietnam, according to new findings presented during a Journal of the American Medical Association media briefing.
“Most low-resource countries do not have adolescent vaccination programs,” Kathleen M. Neuzil, MD, MPH, senior clinical adviser for vaccines and the director of the influenza vaccine project of PATH, Seattle, said during the briefing. “Even if we could design a program, delivering these vaccines on the currently recommended schedules would be challenging. Schedule variations will occur, and do occur, so we need to understand how well these vaccines work in those situations.”
For this reason, Neuzil and colleagues set out to examine more practical and less costly vaccination schedules for the HPV vaccine (Gardasil, Merck) and to determine the immunogenicity and reactogenicity of three alternative dosing schedules of the vaccine. “Our primary hypothesis required that both HPV-16 and HPV-18 serotypes meet noninferiority criteria,” Neuzil said.
The open-label, cluster randomized, noninferiority trial was conducted from October 2007 to January 2010 in Hanoi, Vietnam, and included 903 adolescent girls aged 11 to 13 years.
Twenty-one schools were stratified to four similar school groups; each group was randomly assigned to one of four vaccine schedules. Three doses of the vaccine were delivered on the standard dosing schedule at 0, 2 and 6 months, or one of three alternative dosing schedules — 0, 3 and 9 months; 0, 6 and 12 months; or 0, 12 and 24 months.
Overall, 89.6% of girls received all three doses of the vaccine. The most common adverse event was pain at the injection site.
Girls in the standard therapy group who received all three doses had a serum anti-HPV geometric mean titer of 5,808 (95% CI, 4,961.4-6,799) for HPV-type 16 and 1,729.9 (95% CI, 1,504-1,989.7) for HPV-type 18. Girls who received doses at 0, 3 and 9 months had a mean titer of 5,716.4 (95% CI, 4,876.7-6,700.6) and 1,581.5 (95% CI, 1,363.4-1,834.6) for HPV-types 16 and 18, respectively. Moreover, girls who received doses at 0, 12 and 24 months had a mean titer of 3,692.5 (95% CI, 3,145.3-4,334.9) and 1,335.7 (95% CI, 1,191.6-1,497.3) for HPV-types 16 and 18, respectively.
Noninferiority criteria were met for groups that received doses at 0, 3 and 9 months and 0, 6 and 12 months, but not for the group that received doses at 0, 12 and 24 months.
“The option of delivering HPV vaccine on flexible schedules will allow countries to minimize costs and maximize feasibility according to local vaccination practices,” Neuzil said.
Disclosure: This study was funded with a grant from the Bill & Melinda Gates Foundation. Merck provided the vaccine and the immunogenicity testing at no charge.
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