Parents are hesitant to have their own children vaccinated against the Human Papilloma Virus at the appropriate age — 11 to 12 years — despite approving of the age guidelines recommended by the Centers for Disease Control and Prevention, a new study from the Yale School of Public Health finds.

Researchers interviewed parents of adolescents about the HPV vaccine in order to find out why rates of vaccination are so low, especially when compared to rates for other middle school vaccines. Their work highlighted a paradox: Parents supported the vaccine, even the recommended ages of 11 to 12 years, but preferred to delay vaccination until their child was sexually active.

Eugene Shapiro, senior author of the paper and professor of pediatrics and epidemiology at the School of Public Health, said they found a disconnect between HPV vaccine support and a desire to delay vaccination for their own children. What they approved of in theory did not translate into practice.

“There’s a big gap between scientific … understanding and people’s behavior,” Shapiro said.

The HPV vaccine was the first immunization against cancer, protecting patients from both cervical cancer and genital warts. Despite its effectiveness and safeness in disease prevention, HPV vaccine uptake rates are remarkably low in the United States.

Deputy Director of the Yale Cancer Center Daniel DiMaio pointed out that countries like Australia and the United Kingdom are seeing nationwide declines in the rates of genital warts and cervical precancer dysplasia, a type of abnormal cell growth. According to the CDC, the uptake rate for the HPV vaccine in the U.S. would be 91.3 percent if administered alongside other middle school vaccines. Currently, the uptake rate for the HPV vaccine in the U.S. is 33.4 percent, as of 2011. In the United Kingdom and Australia, that number is 60.4 percent and 71.2 percent, respectively, according to the National Institutes of Health.

“The vaccine works great when it’s widely distributed,” DiMaio said. “In the U.S., we are not doing a particularly good job.”

Unlike previous quantitative survey studies, this study used semi-structured interviews to qualitatively investigate why coverage rates are so low. It also focused on parents, who play a key role along with pediatricians in the vaccination of children.

“We’re trying to get at what [parents] think and why the uptake isn’t better,” Shapiro said.

The contradiction between approval of the recommended age guidelines and simultaneous preference for vaccine delay needs to be resolved by pediatricians taking the time to discuss vaccinations with parents, said Andrea Asnes, director of the Yale Pediatric Residency Program.

According to Director of the Breast Center in the Smilow Cancer Hospital Anees Chagpar, the next step in the research includes studying public health interventions and measuring changes in perception and behavior.

“The most helpful [way] would be to actually look at an intervention to make a difference. What could we do that could change the outcomes?” she said, adding that she believes interventions will “move the field forward in a tangible way.”

There are two versions of the HPV vaccine — Gardasil and Cervarix.

Correction: Jan. 28

A previous version of the article “A paradox of approval with the HPV vaccine” misstated the gender of Anees Chagpar. It also mistakenly stated that Cervarix, an HPV vaccine, can only be used by women, when in fact, both genders may use it.