Merck has successfully gotten 25 percent of girls ages 13 to 17 vaccinated with its HPV vaccine Gardasil, data released by the Centers for Disease Control and Prevention showed.

The HPV vaccine intended to prevent cervical cancer has gotten recommendation by the CDC for girls ages 11 and 12. Many states have responded to the recommendation influenced by Merck or not to require that school girls get Gardasil before the age of 11 years.

Merck has been extremely aggressive in lobbying state governments to mandate the sexually transmitted viral infection in girls age younger than 12, leading to concerns in many medical rights advocates who said states should never mandate any vaccination against the sexually transmitted disease.

A health observer suggested that many of those whose daughters got vaccinated might not have known much about the vaccine in terms of its safety and efficacy. And in fact, there is some doubt in the scientific community about the efficacy and safety of this HPV vaccine.

First of all, females enrolled in the vaccine trials were mostly aged more than 13. Only a very small fraction of the participants were younger than that age, meaning the efficacy and safety for the girls ages younger than 13 remains largely unknown.

Only short-term trials have been conducted and the overall efficacy and safety of this Gardasil remains unknown. The immunity against HPV requires a girl to get three shots at a cost of $375 per person. But it is unknown whether or not a booster shot is needed even if the vaccine is effective in a short-term. Deaths resulting from cervical cancer occur often after the age of 40. How could the vaccine maintain the immunity for next 30 years if an individual gets it at age 11 remains unknown.

Some people questioned the necessity to get the vaccine in the first place. About 4,000 women die from cervical cancer each year, a risk that is too low to justify the expensive vaccination. In the U.S. the risk of dying from cervical cancer is far much less than the risk of dying from traffic accidents. Some experts from a leading medical school have questioned this in a major medical journal suggesting that it is not worth it to get the protection because it is too expensive.

Most people can clear the HPV or human papillomavirus in two years. The virus can persist in only a very small percentage of people raising their risk of cervical cancer.

Merck's HPV vaccine is not omnipotent. It protects against a couple of strains that cause about 70 percent of cervical cancer. Doctors and the U.S. government have said that those who have received the vaccine are not immune to other HPV strains meaning they are still facing the risk and they should keep receiving Pap Smear screening just like those who have not received the vaccine.

While the efficacy and safety of Gardasil is not fully understood, many severe adverse reactions including many cases of deaths have been reported associated with the vaccine shots.

For more information on HPV and the vaccine, read a doc by the CDC.