Human papillomavirus (HPV) is the most commonly sexually transmitted disease in the United States. Close to 20 million Americans between the ages 15 and 49 are infected with the virus.
More than 100 different subtypes of HPV exist, with only a few considered high-risk. Two available vaccines (Cervarix and Gardasil) fight the two most common HPV types that cause cervical cancer. Gardasil also protects against the two most common HPV types that cause genital warts.
The HPV vaccine is most effective when given before sexual activity has begun. The U.S. Centers for Disease Control and Prevention (CDC) recommends that boys and girls get the full three doses of the vaccine starting at age 11 and 12.
However, according to a new study from Sweden, two doses -- not the recommended three -- of the HPV vaccine may be enough to protect against genital warts.
Researchers studied the occurrence of genital warts because it is the earliest measurable prevented disease outcome for the HPV vaccine. The study looked at the health records of more than one million females age 10-24, using Sweden's national health registry. They were followed between 2006 and 2010.
About 30 percent received at least one dose of the HPV vaccine. About 80 percent of those who were vaccinated received all three doses.
Of more than 20,000 cases of genital warts, only 322 occurred after a female had received at least one dose of the vaccine, researchers found.
The females who received only two doses of vaccine had 59 more cases of genital warts per 100,000 person-years compared to those who received three doses.
“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,” lead researcher Lisen Arnheim-Dahlstrom, associate professor at the Karolinska Institute said, according to ScienceDaily.com.
Researchers warn that their study only accounts for genital warts outcomes, not cervical cancer.
Fewer vaccine doses would be good news for health care providers.