TALLAHASSEE — The sponsor of a bill that would require girls entering middle school in Florida to be vaccinated against a sexually transmitted disease that causes cervical cancer said Tuesday he plans to change his bill so that it would take effect a year later.

Sen. Mike Fasano, R-New Port Richey, also said he would amend the bill to make the Department of Health write a rule requiring the girls to receive the vaccine, Gardasil, rather than have the mandate come directly from the legislature. This would allow doctors, scientists and parents to weigh in during the rule-making process.

Fasano's changes came as the vaccine's maker, Merck and Co. Inc., said it would stop trying to get state legislatures to require its use, according to The New York Times.

"I don't want to push people into a situation they feel uncomfortable in doing," Fasano said of his plan to delay when his bill would go into effect from the 2008-09 school year to the 2009-10 school year. "I want to make sure our parents are well-versed understanding what this vaccine is and why we're mandating it."

Florida is one of at least 20 states that are considering making use of the vaccine mandatory for schoolgirls, and the governor of Texas, Rick Perry, has already done so through an executive order. Part of the state rush to embrace the new vaccine has been fueled by Merck lobbying that began even before federal regulators approved the product last year.

The vaccine prevents women from getting cervical cancer and genital warts caused by certain types of the human papilloma virus, but is only effective if taken before a girl or woman is exposed to the virus.

HPV is transmitted through genital contact and affects more than half of the population of sexually active men and women at some point, according to the Centers for Disease Control and Prevention.

Conservative Christians and others have objected to states requiring the vaccine, because they believe it will encourage children and unmarried women to engage in premarital sex. They also question possible side effects of the vaccine, which was approved by the Food and Drug Administration in June and is recommended by federal health officials for girls ages 11 and 12.