Contenders in the Republican presidential contest have been going after presumed front-runner Rick Perry for a number of reasons, but they’ve focused in on one issue that truly seems to resonate with conservatives — the HPV vaccine.

The issue came to the forefront on Monday, when Rep. Michele Bachmann and former Sen. Rick Santorum took Perry to task not only for issuing an executive order mandating that all six-grade girls in Texas be vaccinated against the sexually transmitted human papillomavirus, but also for taking $30,000 in contributions for pharmaceutical giant Merck, which makes the only available vaccine. Bachmann even went as far as to claim that the vaccine could cause mental retardation, despite scientific claims to the contrary.

As that debate rages, the District and Virginia remain the only jurisdictions in the country that mandate the vaccine for girls entering the sixth grade, though earlier this year the Virginia House of Delegates voted to eliminate the state’s requirement. (The State Senate didn’t join them.) When the measure was introduced by Councilmember David Catania (I-At Large) in 2007, it only made it through the entire D.C. Council when an parental opt-out provision was included.

Debate over the wisdom of the HPV vaccine has continued even locally, with some parents and medical groups contesting how effective it is and warning of potential unknown side-effects. During testimony before the council’s Committee on Health, Emily Tarsell explained how her 21-year-old daughter Christina died in her sleep after receiving two of the three shots of the Gardasil regimen. And despite reports that the vaccine is 100 percent effective against two strains of HPV that can cause cervical cancer, many parents — locally and nationally — say that the requirement undermines their parental authority and could lead their daughters to be sexually active at an earlier age.

According to information provided by Catania’s office, those doubts seem to have led many parents in the District to refuse to let their daughters be vaccinated. As of April 2011, only 22 percent of sixth-grade girls in D.C. public schools were in the midst of or had completed the vaccinations; percentages stood at 19, seven and eight for charter, private and parochial schools, respectively. The numbers were only slightly higher for seventh-grade girls in the District — 28 percent in public schools, 22 percent in charter schools, and 13 percent each for private and parochial schools.