Ads for the Gardasil Vaccine shows girls saying they want to be "one less" victim of Cervical Cancer.

But Cervical Cancer takes years to develop... so Gardasil's ultimate effectiveness is still unknown.

Gardasil debuted in 2006 as the first real anti-cancer vaccine and an easy way to reduce young girls' risk of developing deadly cervical cancer.

But two years later, some still experts have lingering questions about Gardasil.

How well will it actually prevent Cervical Cancer?

The final answer won't be known for decades.

Preliminary evidence suggests the Gardasil is highly effective at reducing pre-cancerous lesions.

But full-blown Cervical Cancer takes many years to develop, so the true test is yet to come.

Girls' immunity may wear off over time, making booster shots necessary.

Experts estimate that even if the vaccine protects women for 10 years at a time, it may not be cost effective.

That's partly because Gardasil does not protect against all viruses that cause Cervical Cancer, so women must still spend time and money on regular screenings.

Researchers say girls should probably still get the vaccine because some immunity is better than none - but they caution against worldwide mandates for vaccination, saying Gardasil has many years ahead before its success is fully established.

The "Centers For Disease Control" and prevention estimates about six-point-two million Americans become infected with HPV each year.