Gov. Rick Perry signed an order Friday making Texas the first state to require that schoolgirls be vaccinated against the sexually transmitted virus that causes cervical cancer.

By issuing an executive order, Perry apparently sidesteps opposition in the Legislature from conservatives and parents' rights groups who fear such a requirement would condone premarital sex and interfere with the way parents raise their children.

Beginning in September 2008, girls entering the sixth grade will have to get Gardasail, Merck & Co.'s new vaccine against strains of the human papillomavirus, or HPV.

Perry, a conservative Christian who opposes abortion and stem-cell research using embryonic cells, counts on the religious right for his political base. But he has said the cervical cancer vaccine is no different from the one that protects children against polio.

"The HPV vaccine provides with with an incredible opportunity to effectively target and prevent cervical cancer," Perry said in announcing the order.

Merck is bankrolling efforts to pass state laws across the country mandating Gardasil for girls as young as 11 or 12. It doubled its lobbying budget in Texas and has funneled money through Women in Government, an advocacy group made up of female state legislators around the country.

Perry has several ties to Merck and Women in Government. One of the drug company's three lobbyists in Texas is Mike Toomey, Perry's former chief of staff. His current chief of staff's mother-in-law, Texas Republican state Rep. Dianne White Delisi, is a state director for Women in Government.

Perry also received $6,000 from Merck's political action committee during his re-election campaign.

Parents can have their daughters opt out of the inoculations by filing an objection on religious or other philosophical grounds. Even with such provisions, however, conservative groups say such requirements interfere with parents' rights to make medical decisions for their children.

The federal government approved Gardasil in June, and a government advisory panel has recommended that all girls get the shots at 11 and 12, before they are likely to be sexually active.

The vaccine is too new to know how long protection will last, according to the federal Centers for Disease Control and Prevention. Studies have followed women for five years and found that they are still protected. More research is being done to find out how long protection will last, and if a booster vaccine is needed years later.

That uncertainty adds to conservatives' oppositon.

The New Jersey-based drug company could generate billions in sales if Gardasil — at $360 for the three-shot regimen — were made mandatory across the country. Most insurance companies now cover the vaccine, which has been shown to have no serious side effects.

Merck spokeswoman Janet Skidmore would not say how much the company is spending on lobbyists or how much it has donated to Women in Government. Susan Crosby, the group's president, also declined to specify how much the drug company gave.

A top official from Merck's vaccine division sits on Women in Government's business council, and many of the bills around the country have been introduced by members of Women in Government.