RICHMOND, Feb. 27 -- Virginia Gov. Timothy M. Kaine said Tuesday he has "some qualms" about a recently approved law that seeks to have sixth-grade girls immunized against a virus that causes cervical cancer.

This month, the Virginia General Assembly became the first legislative body in the country to mandate that girls receive the human papillomavirus vaccine before they enter high school.

The vaccine protects against several strains of the sexually transmitted virus that causes nearly 7,000 cases of cervical cancer annually.

Speaking on WTOP radio, Kaine (D) said he might try to amend the bill to include "a generous opt-out" provision so parents have greater authority to decide whether they want their child vaccinated.

Kaine has until March 26 to decide whether he will sign, veto or amend the legislation.

"We mandate a lot of vaccines for schoolchildren . . . for infectious diseases. This goes an additional step. It is not something we are mandating to stop infections among school kids," said Kaine, who later added, "I think the opt-out provision to protect kids and parents should be generous."

As it was approved, the legislation includes a provision that requires parents to be given information about the vaccine before it is administered. They could then request that their child not receive it.

Del. Phillip A. Hamilton (R-Newport News), sponsor of the legislation, said he is not sure how the governor could make the opt-out provision any stronger.

"Right now, parents are given information, and if they choose not to do it, they don't have to do it. They just have to sign a form so the health department knows they opted out," Hamilton said. "I just don't know how much broader you can make it."

Merck and Co., a New Jersey-based pharmaceutical maker, received federal approval in June to sell the vaccine, which is called Gardasil.

Merck then began a nationwide lobbying campaign to try to get states to mandate the vaccine. At least 20 states are considering doing so.

But Merck suspended the campaign two weeks ago amid questions about whether profit, rather than public health, is guiding the debate. Concerns have also been raised about potential side effects.

Because the virus is transmitted through sexual contact, some parents and politicians worry that mandating the vaccine might encourage promiscuity.

Although social conservatives tried to derail the legislation in the General Assembly, it passed with overwhelming bipartisan support.