HPV Infection Rate Down After Vaccine Approval

The prevalence of infection with cancer-causing strains of human papillomavirus (HPV) declined among women during the period that coincided with the introduction of HPV vaccine, investigators reported here.

The rates of infection with HPV 16 and HPV 18 have declined since July 2007, a year after the first vaccine was introduced, including a significant decrease in HPV 16 infection (P=0.0012).

Four other HPV subtypes, including the other two targeted by the quadrivalent vaccine (Gardasil), also declined significantly. Overall, the rate of infection with any HPV subtype has decreased since mid-2007 among, according to HPV test results for 57,262 women.

Because the women's vaccination status was unknown, the decline could not be linked definitively to the vaccines, Elizabeth Dickson, MD, said at the Society of Gynecologic Oncology meeting.

"[The decline] could be because of the vaccine," Dickson, of the University of Minnesota in Minneapolis, told MedPage Today. "It could just be that the natural history of the HPV types is changing and that the milieu of the types of HPV in women's samples is changing over time."

What is genital HPV infection? Genital human papillomavirus (also called HPV) is the most common sexually transmitted infection (STI). There are more than 40 HPV types that can infect the genital areas of males and females. These HPV types can also infect the mouth and throat. Most people who become infected with HPV do not even know they have it.

HPV is not the same as herpes or HIV (the virus that causes AIDS). These are all viruses that can be passed on during sex, but they cause different symptoms and health problems.

"But it's an interesting finding because, even though we didn't know their vaccination status, the HPV types in the vaccine are going down," she said.

- This study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal. - The prevalence of infection with cancer-causing strains of human papillomavirus (HPV) declined among women during the period that coincided with the introduction of HPV vaccine. - Four other HPV subtypes, including the other two targeted by the quadrivalent vaccine (Gardasil), also declined significantly.

According to the CDC, about 40 types of HPV have been linked to genital infection. Interest in individual HPV strains has increased because of recognition that specific strains are more closely associated with cervical cancer (HPV 16 and 18) and with genital warts (HPV 6 and 11) than are other subtypes.

Numerous studies have documented the uptake of the HPV vaccines, but information about temporal trends in HPV infection with specific strains has been scarce.

Dickson and colleagues sought to document patterns of HPV infection, focusing on the 18 most prevalent types. They analyzed specimens obtained from women who participated in cervical cancer screening programs (including HPV testing) during 2004 to 2011. Participants' ages ranged from 11 to 29 at the time of testing.