TORONTO – A new study offers some hope that two doses of HPV vaccines may work as well as the current regimen of three.

In recent years two new vaccines have come the market that protect against human papillomaviruses which cause cervical cancer, head and neck cancers and some other urogenital cancers.

But the vaccines are given in three doses and are expensive, costing between $400 and $500 per child.

All Canadian provinces and territories currently offer the vaccine for free to girls, but there have been calls to widen the programs to include boys as well.

A new Canadian study looks at whether the dosing schedule could be changed to drop one of the shots — a move that would save substantial amounts of money.

It suggests that two doses in pre-adolescent girls works as well as three doses in girls in their later teens and early 20s, but says more study is needed.

The lead author, Dr. Simon Dobson, says it’s still not clear how long the protection of two doses will last and whether another booster shot would be required down the road.

The vaccine used in the study was Gardasil, which is made by Merck Canada. It protects against two strains of HPV that cause cancer and two that cause genital warts.

Another vaccine, Cervarix, protects against the two cancer-causing strains as Gardasil. Cervarix is made by GlaxoSmithKline. Other studies that looked at Cervarix have found similar results to the question of whether two doses might be sufficient.

The new study is being published in the Journal of the American Medical Association.