New research suggests that a single dose of the human papillomavirus vaccine could be enough to protect women against cervical cancer. This is according to a study published in the journal Cancer Prevention Research.

According to the Centers for Disease Control and Prevention (CDC), around 79 million Americans are infected with the human papillomavirus (HPV), and approximately 14 million people will become infected each year.

Every year, around 26,000 new cancers occur in the US as a result of HPV, says the CDC. Of these, 18,000 are among women, and 11,500 are cases of cervical cancer.

There are currently two HPV vaccines available that protect against the HPV infections, which can cause cervical cancer - Gardasil and Cervarix.

Current guidelines recommended that these vaccines should be administered for girls in a series of three shots at age 11 or 12, or for girls aged 13 to 26 who have not yet been vaccinated.

However, a CDC report release this year detailing the vaccination coverage among adolescent girls between 2006 and 2013, revealed that only 53.8% of girls aged between 13 and 17 had the HPV vaccine, and of these, only 33.4% had all three doses.

From this, researchers from the US, Costa Rica, the Netherlands and France set out to determine whether one or two does of the Cervarix HPV vaccine may have similarly protective effects against HPV.

Using data from a phase III trial funded by the National Cancer Institute (NCI) to test the effectiveness of Cervarix in women from Costa Rica, the researchers found that around 20% of these women had not received the full three doses of the HPV vaccine.

The researchers then measured the antibody levels in blood samples from the women, in order to detect presence of an immune response to the vaccine. The blood samples were taken from 78 women who received one dose of the vaccine, 192 women who received two doses, and 120 women who received three doses.

100% immunization found 'even with one dose'

The results revealed that 100% of these women in all three groups showed the presence of antibodies against HPV 16 and 18 - the two HPV types that can cause cervical cancer - for up to 4 years.

Although antibody levels were lower from the women who received one dose, compared with those who received three doses, the levels still appeared stable.

The researchers note that these findings suggest the preventive effects of even one dose of the vaccine are long-lasting.

Furthermore, it was found that antibody levels in women who received one or two doses of the HPV vaccine were 24 times higher, compared with women who did not receive the vaccination at all but who had HPV infection previously.

Potential for reduced HPV vaccination dosage

Mahboobeh Safaeian, of the Division of Cancer Epidemiology and Genetics at the NCI, says their findings "challenge previous dogma" that these vaccines need multiple doses to achieve long-term effectiveness.

She adds:

"Our findings suggest promise for simplified vaccine administration schedules that might be cheaper, simpler, and more likely to be implemented around the world.

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% of cervical cancers occur, and where cervical cancer is one of the most common causes of cancer-related deaths."

Safaeian says that in some parts of the world, such as Chile and British Columbia, two doses of the HPV vaccine is already within the standard recommended vaccination program.

But she notes that although these study findings show that one does of the vaccine also provides long-term effects, further research is needed before any policy guidelines can be changed.

"For instance," she adds, "it is important to note that persistence of antibody responses after a single dose has not been evaluated for Gardasil, the quadrivalent HPV vaccine that is more widely used in the United States and many other countries."

Earlier this year, Medical News Today reported on research suggesting that parents' worries regarding the HPV vaccine prevent girls from receiving it.