The U.S. Food and Drug Administration denied Merck & Co Inc.’s request to market its cervical cancer vaccine Gardasil to women age 27 to 45 due to certain “issues” that preclude approval within the expected review time frame, a letter of the agency read.

Gardasil is currently approved in the U.S. for use in girls and women aged 9 to 26 to block four types of human papilloma virus, a sexually transmitted virus, which can cause cervical cancer and genital herpes.

Merck made it clear that the letter from the FDA has no impact at all on Gardasil for women aged 9 through 26. Initially, the company expected the drug’s approval in older woman by next month. Instead, the company will respond to the FDA next month, thus missing the approval timeframe.

The letter does not specify what the exact “issues” were standing in the way of approval. However, the FDA move is seen as negative, causing Merck’s shares to drop 1 percent to 36.68, according to CNNMonney.com.

Currently Gardasil is the only cervical cancer vaccine on the market. It has racked up about $1 billion in sales since its June 2006 U.S. launch.

Cervical cancer is the second most common cause of cancer death in women worldwide, resulting in nearly a half-million diagnoses and 280,000 deaths each year. In 2007, there were an estimated 11,000 new cases of cervical cancer and 3,600 deaths in the US.

About 6.2 million men and women become infected with HPV every year in the U.S. and approximately 20 million people are currently infected. Experts warn that even though the vaccine is purely preventive, it does not cure an existing HPV infection, but can prevent future infections. That is why is recommended that girls get the vaccine before they are sexually active.