HealthDay News — Incomplete immunization with three doses of quadrivalent human papillomavirus vaccine (HPV) instead of the recommended four still appears to offer some protection against the disease, according to researchers.

Compared with no vaccination, two doses of HPV vaccine offered 72% protection against condyloma, or genital warts, Lisen Arnheim-Dahlström, PhD, of the Karolinska Institute in Stockholm, and colleagues reported in the Journal of the American Medical Association.

Vaccination with the full three dose series offered the best protection at 82%, results from the population-based Swedish study indicate.

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Although typically benign, condyloma are the “the earliest measurable preventable disease outcome,” the researchers noted, adding the more study is necessary to determine the effect of incomplete HPV vaccine series on cervical cancer risk.

Girls who receive the quadrivalent human papillomavirus (HPV) vaccine before 17 years of age can get considerable protection from warts after two doses, although maximum protection is observed after the recommended three doses, according to a study published in the Feb. 12 issue of the Journal of the American Medical Association.

For the current study, the researchers used registry data from medical records and prescription information to determine the incidence of condyloma among 1,045,165 women aged 10 to 24 years living in Sweden, who received the quadrivalent HPV vaccine.

During the 3,995,631 person-years of follow-up, the researchers identified 20,383 cases of condyloma.

Among those who were first vaccinated at age 10 to 16 years, the incidence rate ratio was 0.31 for one dose, 0.29 for two doses and 0.18 for three doses compared with no vaccination. Per 100,000 person-years, the incidence rate difference was 384 for one dose, 400 for two doses, and 459 for three doses.

“Although maximum reduction in condyloma risk was seen after receipt of three doses of quadrivalent HPV vaccine, receipt of two vaccine doses was also associated with a considerable reduction in condyloma risk,” the researchers concluded.

The study was funded by the Swedish Foundation for Strategic Research. Arnheim-Dahlström reported financial links with GlaxoSmithKline, Merck and Sanofi Pasteur Merck Sharp Dome.


  1. Herweijer E et al. JAMA 2014; 311(6): 597-603.