TRENTON, N.J. - Pediatricians, gynecologists and even health insurers all call Gardasil, the first vaccine to prevent cervical cancer, a big medical advance.

But medical groups, politicians and parents began rebelling after disclosure of a behind-the-scenes lobbying campaign by Gardasil's maker, Merck & Co., to get state legislatures to require 11- and 12-year-old girls to get the three-dose vaccine as a requirement for school attendance.

Some parents' groups and doctors particularly objected because the vaccine protects against a sexually transmitted disease, human papilloma virus, which causes cervical cancer. Vaccines mandated for school attendance usually are for diseases easily spread through casual contact, such as measles and mumps.

Bowing to pressure, Merck said Tuesday that it is immediately suspending its controversial campaign, which it had funded through a third party.

"Our goal is about cervical cancer prevention, and we want to reach as many females as possible with Gardasil," Dr. Richard M. Haupt, Merck's medical director for vaccines, told The Associated Press.

"We're concerned that our role in supporting school requirements is a distraction from that goal, and as such have suspended our lobbying efforts," Haupt said, adding the company will continue providing information about the vaccine if requested by government officials.

Whitehouse Station-based Merck launched Gardasil, the first vaccine to prevent cervical cancer, in June. It protects against the two virus strains that cause 70 percent of cervical cancer and two strains that cause most genital warts.

Sales totaled US$235 million through the end of 2006, according to Merck.

Last month, the AP reported that Merck was channeling money for its state-mandate campaign through Women in Government, an advocacy group made up of female state legislators across the country.

Conservative groups opposed the campaign, saying it would encourage premarital sex, and parents' rights groups said it interfered with their control over their children.

Even two of the prominent medical groups that supported broad use of the vaccine, the American Academy of Pediatricians and the American Academy of Family Practitioners, questioned Merck's timing, Haupt said Tuesday.

"They, along with some other folks in the public health community, believe there needs to be more time," he said, to ensure government funding for the vaccine for uninsured girls is in place and that families and government officials have enough information about it.

Legislatures in roughly 20 states have introduced measures that would mandate girls have the vaccine to attend school, but none has passed so far. However, Texas Gov. Rick Perry on Feb. 2 issued an executive order requiring Texas girls entering the sixth grade as of 2008 get the vaccinations, triggering protests from lawmakers in that state. Parents there could opt out for their daughters if they state religious or philosophical objections, but several Texas lawmakers want to have parents opt in instead of opting out.

Perry defended his order Tuesday, a day after lawmakers in Austin held a lengthy hearing on the issue but failed to act on a bill to override the order.

Dr. Anne Francis, who chairs an American Academy of Pediatrics committee that advocates for better insurer reimbursement on vaccines, called Merck's change of heart "a good move for the public."

"I believe that their timing was a little bit premature," she said, "so soon after (Gardasil's) release, before we have a picture of whether there are going to be any untoward side effects."

Given that the country has been "burned" by some drugs whose serious side effects emerged only after they were in wide use, including Merck's withdrawn painkiller Vioxx, Francis said, it would be better to wait awhile before mandating Gardasil usage.

She said she also was concerned about requiring a vaccine for a disease that is not communicable and so does not have a big public health impact. While doctors expect Gardasil to have a huge effect in poor countries where women do not get Pap smears, in this country those tests limit the incidence of cervical cancer to about 9,710 new cases and 3,700 deaths each year.

The National Vaccine Information Center has been publicizing reports of side effects -- mostly dizziness and fainting -- in several dozen people getting Gardasil, which is approved for use in females ages 9 to 26. The center, a group of parents worried that vaccines harm some children, questions whether the vaccine was tested in enough young girls.

Officials with the Centers for Disease Control and Prevention, however, say that reports of side effects through the end of January don't raise any red flags.

The vaccine also is controversial because of its price -- $360 for the three doses required over a six-month stretch. Because of that cost and what pediatricians and gynecologists say is inadequate reimbursement by insurers, many are choosing not to stock the vaccine or requiring surcharges to administer it, increasing the cost for many families and making the vaccine hard to come by.

Merck shares fell 37 cents to $44.13 in after-hours trading Tuesday after rising 22 cents to close at $44.50 on the New York Stock Exchange.