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CDC HIV/AIDS/Viral Hepatitis/STD/TB Prevention News Update
CANADA: 2 Doses of HPV Vaccine in Girls May Offer Similar Protection as 3 Doses in Young Women
Staff Writer
May 1, 2013
Infection Control Today (04.30.2013) Aids Weekly Plus

Results of a recent study by Simon R.M. Dobson, MD, and colleagues at the University of British Columbia in Vancouver, Canada, indicated that girls who received two doses of human papillomavirus (HPV) vaccine had immune responses to HPV-16 and HPV-18 infection noninferior to those of young women who received the usual three doses of the vaccine. They also examined antibody levels to two other strains of the virus, HPV-6 and HPV-11 and compared girls given two or three doses. The researchers conducted the randomized, phase 3, multicenter study of 830 Canadian females from August 2007 through February 2011. Researchers also collected blood samples from 675 participants (81 percent) for follow up. The 261 girls ages 9–13 years received three doses of quadrivalent HPV vaccine at 0, 2, and 6 months; and 259 girls received two doses at 0 and 6 months. The 310 young women ages 16–26 years received three doses of vaccine at 0, 2, and 6 months. Researchers measured antibody levels at 0, 7, 18, 24, and 36 months. Antibody levels in girls given two doses were noninferior to those of women given three doses for all four HPV genotypes. Girls given two doses versus three doses had noninferior antibody response for all four vaccines. The antibody levels for girls given two doses compared to women given three doses remained noninferior for all genotypes for 36 months. However, antibody responses in girls given two doses compared to those of girls given three doses for all four vaccine genotypes were noninferior at month 7, but not for HPV-18 by month 24, or HPV-6 by month 36. The authors note that more data on the length of protection are needed before they can recommend reduced dose schedules of the vaccine. The full report, “Immunogenicity of 2 Doses of HPV Vaccine in Younger Adolescents vs 3 Doses in Young Women: A Randomized Clinical Trial,” was published in the journal JAMA (2013; 309(17):1793–1802).