HPV vaccine effective in one dose
November 4, 2013

HPV Vaccine Effective In Just A Single Dose, Says Study

Brett Smith for redOrbit.com - Your Universe Online

An HPV vaccine that guards against cervical cancer was shown to be effective in just one dose, instead of the recommended three, according to a new study published by the journal Cancer Prevention Research. The study researchers found that one dose of the vaccine for human papillomavirus (HPV), the disease known to cause cervical cancer, established antibodies that remained stable in the blood for four years. The team said their study was good news for protecting women against a form of life-threatening cancer.

"The latest Morbidity and Mortality Weekly Report from the Centers for Disease Control and Prevention on vaccination coverage indicates that in 2012, only 54 percent of girls between 13 and 17 years old initiated HPV vaccination, and only 33 percent of them received all three doses," said study author Mahboobeh Safaeian, an epidemiologist and geneticist at the National Cancer Institute (NCI) in Bethesda, Maryland.

"We wanted to evaluate whether two doses, or even one dose, of the HPV 16/18 L1 VLP vaccine (Cervarix) could induce a robust and sustainable response by the immune system," she added. "We found that both HPV 16 and HPV 18 antibody levels in women who received one dose remained stable four years after vaccination. Our findings challenge previous dogma that protein subunit vaccines require multiple doses to generate long-lived responses."

The study team used data from a clinical trial of the Cervarix vaccine on Costa Rican women. Although the trial called for three doses, 20 percent of participants received fewer doses for a wide range of reasons.

The scientists discovered that antibody levels were lower for women who received one dose than for those women who received the recommended three doses. However, the antibody levels in the one- and two-dose women were five to 24 times greater than levels for a control group of women who were not vaccinated but had previously contracted HPV.

"Our findings suggest promise for simplified vaccine administration schedules that might be cheaper, simpler, and more likely to be implemented around the world," said Safaeian. "Vaccination with two doses, or even one dose, could simplify the logistics and reduce the cost of vaccination, which could be especially important in the developing world, where more than 85 percent of cervical cancers occur, and where cervical cancer is one of the most common causes of cancer-related deaths."

On Sunday, pharmaceutical giant Merck had more good news in the battle against cervical cancer, announcing encouraging results from clinical trials for a new HPV vaccine.

Merck told the Wall Street Journal that the study results maintain its plan to put forward the new vaccine, dubbed V503, for regulatory approval by the end of 2013, which could result in the vaccine being available next year.

According to Merck, the vaccine “prevented approximately 97 percent of cervical, vaginal and vulvar pre-cancers caused by HPV types 31, 33, 45, 52, and 58.”

Regardless of which vaccines might be in use in the coming months, many women are not receiving any vaccination against HPV, thus placing them at unnecessary risk according to many experts. A recently published UK-based study found that minority women are less likely than their white counterparts to get vaccinated.

"It's vital that girls, along with their parents, understand the importance of both these programs, which are designed to prevent cancer from developing,” Sara Hiom, Cancer Research UK's director of early diagnosis, told BBC News. "As well as cervical cancer, research has shown that HPV also increases the risk of developing other cancers, such as some types of mouth, head and neck cancers, anal cancer and other genital cancers."