Gardasil, the vaccine that protects against human papilloma virus (HPV) and cervical cancers that result from such infections, may be more powerful than previously thought.

A new study published in the Journal of the American Medical Association has shown that two vaccinations are as effective as three in bringing the immune system up to speed to produce protective antibodies.

The study examined 259 Canadian girls between the ages of 9 and 13 who had been given only two doses of the vaccine six months apart. When researchers looked at the levels of antibodies against two types of HPV that the immunizations protect against, they found it matched the levels found in girls in women aged 16-26 who had received three doses.

The girls who had two doses of the vaccine retained the same level of protection for two and three years after the last vaccination compared to women who were given three doses.

The problem arose when young girls who had received two vaccinations were compared to other pre-teen girls that had three doses. After two years, those that received three immunization had higher levels of protective antibodies for two HPV types than girls who had only received two immunizations.

Despite this caveat, the researchers suggested that a two-dose vaccination program should be made standard for girls in their pre-teen years. They suggested for a booster to be given in late teen years to "provide a high level of antibody through early adulthood."

A supplementary editorial to the study, written by Jessica Kahn, MD, MPH, and David Bernstein, MD, MA, both from the Cincinnati Children's Hospital Medical Center, stated that the study did not have data on girls between the ages of 13 and 16. They continued that the benefit of a two dose schedule would he inherent cost reduction in using one less vaccination, making patients more likely ot get vaccinated.

The reseachers will follow participants for ten years to determine long term protection in two doses versus three doses.

A video by the primary author explaining the trial can be found here.