Oct. 22 (Bloomberg) -- Merck & Co.'s Gardasil, a vaccine to prevent cervical cancer, wasn't linked to an increased risk of blood clots or other serious conditions in the first controlled U.S. study since the vaccine was recommended two years ago.

The Centers for Disease Control and Prevention's Immunization Safety Office said today in Atlanta that its study of 370,000 doses given to girls and young women over the past two years didn't find evidence that the vaccine is dangerous, contradicting claims by some advocacy groups.

Critics, among them groups promoting abstinence before marriage, have said the vaccine may not be safe and gives women a false sense of security about sexually transmitted diseases. The CDC, which recommends routine vaccination for girls starting at ages 11 and 12, surveyed information from the Vaccine Safety Datalink, which uses medical data to test hypotheses about vaccine safety.

``There were no associations found that suggested an elevated risk,'' said John Iskander, acting director for the Immunization Safety Office, in an interview.

The vaccine was given to about a quarter of teenage girls last year, according to CDC figures. Among women ages 19 to 26, about 15 percent have received the shot, according to a September research report by Merrill Lynch & Co.

Sales Growth

Gardasil had $1.5 billion in sales worldwide in 2007, making it the drugmaker's second-fastest growing product that year. The vaccine's U.S. sales fell 16 percent in the third quarter, Merck of Whitehouse Station, New Jersey said today. The drugmaker has begun targeting marketing for Gardasil to women ages 19 to 26, who have been less likely to get the shots.

Merck fell $1.96, or 6.5 percent, to $28.01 at 4:03 p.m. in New York Stock Exchange composite trading after the company reported that third-quarter profit fell 28 percent and that it planned to cut 7,200 jobs.

The study covered 190,000 girls and young women who received at least one dose of the vaccine's three-shot regimen. Researchers for the CDC compared medical data on those who received the vaccine with data for girls and young women who received other vaccines or none. Gardasil was recommended for use by the CDC's advisory group in June 2006.

``The results are really reassuring,'' said Paul Offit, chief of the infectious diseases division at the Children's Hospital of Philadelphia. ``There's a public perception that the vaccine is not safe. This is important for countering negative information.''

Eight Outcomes

Researchers for the CDC looked at eight specific medical outcomes that might have been linked to use of the vaccine, including seizures, strokes, blood clots and serious neurological side effects, said Iskander. Monitoring will continue, he said.

``Although the findings could change, we're reassured by findings so far,'' Iskander said in an interview. He made a presentation on Gardasil at a CDC advisory panel meeting in Atlanta today.

Gardasil, introduced in 2006, protects against four types of genital human papillomavirus, HPV, which is spread through sexual contact and can cause cervical cancer in women. The vaccine targets forms of the virus linked to 70 percent of cases of cervical cancer.

It's recommended for girls aged 11 and 12, given in a three injections over six months, and approved for use in girls and young women ages 9 through 26.

``The study results are great results that support the safety profile of Gardasil,'' said Richard Haupt, executive director of Merck's clinical research department, in an interview.

To contact the reporter on this story: Aliza Marcus in Atlanta at amarcus8@bloomberg.net

Last Updated: October 22, 2008 16:12 EDT