The debate over whether to require schoolgirls to be vaccinated for HPV, the sexually-transmitted virus that can cause cervical cancer, has barely been engaged. What makes this discussion more interesting — and less predictable — is how blurred the lines are that usually separate advocates and opponents on most public health issues.

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They appear to be following the lead of Texas Gov. Rick Perry, also a Republican, who last month ordered parents in the Lone Star State to march their pre-pubescent daughters to the pediatrician to get a series of three shots aimed at lowering their risk of cervical cancer years from now, when they become sexually active.

However, the two medical groups you'd think would be leading the campaign for vaccination, the American Academy of Pediatrics and the American College of Gynecologists and Obstetricians, seem inclined to slow the mandatory vaccination train down. (The debate is playing out in at least 31 other states — in addition to Georgia and Texas — which is remarkable considering the vaccine was only approved for public use in June.)

What's going on?

While the prevention vs. promiscuity debate generates most of the news coverage and commentary, larger issues demand further study before state legislators make the vaccine mandatory. They include:

The cost: It's not the most expensive vaccine to come along, but it's up there — $360 for the three-shot series. If all Georgia sixth-grade girls were to get it, the cost would be more than $20 million. Nationwide, there are 21 million sixth-grade girls. You do the math.

The benefit: In a large cohort of females between the ages of 16 and 26 who were followed for four years, the vaccine prevented lasting infections from two human papillomavirus strains that cause 70 percent of cervical cancers and two other strains that cause 90 percent of genital warts. But it only works if women haven't already been exposed to those strains. Hence, the push to vaccinate young girls before they become sexually active.

The limitations: Will the vaccine last longer than five years? What are its long-term effects? Answering these questions will take more time and study, which is another reason scientists want to start providing it to young girls now.

The relative value: Last year, 9,700 cases of cervical cancer were reported in the United States, as well as 3,700 deaths. The vast majority of those cases were in patients who had never had a Pap test, or a cervical screening. When detected in early stages, HPV is easily treated and rarely proceeds to cancer, which is why the death rate from this form of cancer has declined steadily for more than a decade.

Making it mandatory: No vaccine, at least one not connected to a potential pandemic, has moved so quickly from approval to being required. And it's anyone's guess how school districts will enforce such a statewide requirement. They barely enforce current requirements for children to get vaccines for mumps, measles and other much more communicable diseases.

More troubling is that Gardasil, the trade name of the vaccine, is manufactured by Merck, which has heavily contributed to Women in Government, a group of female legislators who have been pushing legislation to require the vaccine all over the country. Mandatory vaccination opens a potential $5 billion market to Merck, which wants to get its product out there before a competitor releases a similar vaccine later this year.

The bottom line: The HPV vaccine is an important development in the nation's effort to prevent a form of cancer that infects and kills a small number of women every year. But its significant costs and the uncertainties of its long-term effectiveness more than outweigh making it mandatory at this stage.

A wiser course would be to focus resources on raising awareness about HPV in young women and encourage those who are sexually active to be routinely screened. Meanwhile, public health advocates and legislators should closely monitor Gardasil's effectiveness in teens and young adults who voluntarily agree to try it.

• Mike King is a member of the editorial board. His column runs Thursdays.