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Two HPV vaccine doses significantly reduced risk for condyloma
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Two doses of the quadrivalent HPV vaccine was associated with a reduced risk for condyloma, especially among girls aged younger than 17, according to data published in JAMA.
“When it comes to the vaccine’s ability to protect against genital warts in girls between 10 and 16 years of age, we can see that two doses provide good protection, up to 71%, but that three doses is better, up to 82%,” Lisen Arnheim Dahlström, PhD, of the department of medical epidemiology and biostatistics at Karolinska Institutet in Sweden, said in a press release.
Dahlström and colleagues followed a cohort of more than 1 million girls in Sweden aged 10 to 24 years from 2006 to 2010. The girls were divided into groups according to their HPV vaccine status: those who were unvaccinated and those who received one, two or three doses of the vaccine. The researchers evaluated the incidence of condyloma among the girls.
There were 20,383 incident cases of condyloma during the follow-up period of 3.8 years and among those, 322 occurred after receipt of at least one dose of vaccine. For girls aged 10 to 16 at first vaccination, receiving three doses of the vaccine was associated with an incident rate ratio of 0.18 (95% CI, 0.15-0.22). Receiving two doses was associated with an incident rate ratio of 0.29 (95% CI, 0.21-0.40). The incident rate ratio for one dose was 0.31 (95% CI, 0.20-0.49).
For one dose, the incidence rate difference was 384 cases per 100,000 person-years compared with no vaccination. For two doses, the difference was 400 cases per 100,000 person-years and for three doses, the difference was 459 cases per 100,000 person-years compared with no vaccination.
“Our results suggest that we should continue with the recommended three doses, but open up for a future two-dose schedule after more studies have been conducted regarding the protection against genital warts and initial stages of cervical cancer,” Dahlström said.
Disclosure: Arnheim Dahlstrom and other study researchers have received grants from Merck, GlaxoSmithKline and Sanofi Pasteur MSD.
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