Gardasil protects against infections with dangerous strains of HPV, the sexually transmitted virus that causes cervical cancer and genital warts. The CDC recommends that girls get the vaccine at age 11 or 12 years -- long before they become sexually active.

There have been some speculations about the long-term safety of Gardasil vaccine but two years after Gardasil's approval, safety monitors detected no major safety problems.

There have been some case series recently in Australia raising concern that the vaccine might cause some rare but still serious side effects such as allergic shock and damage to the nervous system. However, reports made at meeting of the Advisory Committee on Immunization Practices (ACIP), showed no such side effects could be linked to the vaccine.

The committee heard four reports on Gardasil's safety:

• The CDC's Vaccine Adverse Event Reporting System (VAERS) finds no link between Gardasil and adverse events reported by doctors and vaccine recipients.

• A continuous, week-by-week CDC analysis of data from eight managed-care organizations finds no sign of adverse events emerging in Gardasil recipients. This Vaccine Safety Datalink (VSD) project finds no "signal" linking Gardasil to eight safety problems, including blood clots, allergic reactions, stroke, seizure, or Guillain-Barre syndrome.

• An independent academic group, the Clinical Immunization Safety Assessment Network (CISA), finds no link between Gardasil and disorders of the central (transverse myelitis) or peripheral (or Guillain-Barre syndrome) nervous systems.

• Merck's registry of women who were inadvertently given Gardasil while pregnant finds no link between the HPV vaccine and birth defects, miscarriages, or infant/fetal deaths.

There have also been reports of syncope - fainting or losing consciousness, in teenage girls receiving Gardasil. Although the syncope is on the rise among teenage vaccine recipients, the phenomenon is not only related to Gardasil but to all teen vaccines.

Family practitioners and pediatricians said that at least one in four parents refused to HPV vaccinate their 11- to 12-year-old girls.

Three major reasons have been reported for refusal:

• Parents worried that Gardasil is "too new."
• Parents said their teenage girl was too young or not sexually active.
• Parents said their insurance didn't cover Gardasil.

Most parents' concerns about Gardasil were not explicitly related to concerns about vaccine safety.