Glaxo said it had answered all the questions raised by the FDA regarding its vaccine and decided that it will add results from further phase III study called HPV-008 to its original application.

The drug maker included interim data from the trial in its application in March 2007, but did not expect the agency would require new studies for approval.

New data from the trial are anticipated to be sent to the U.S. regulator in the first half of 2009 and an FDA decision is expected six months later.

Some analysts estimated that the sales for Cervarix in 2009 would be $ 150 million.   But Morgan Stanley analysts were cited by Reuters as predicting last month that Galxo's Cervarix would not get approved in the U.S. until 2014.

The delay boosted the stock of Merck & Co Inc. by 3 percent today. Merck sells the similar vaccine called Gardasil, which earns the company an estimated $1.5 billion each year in the United States.

With states mandating school girls to get vaccinated with this drug, analysts predicted the annual sales for Gardasil can reach up to $3 billion.

Cervarix is like Merck's vaccine indicated for prevention against cervical cancer in young females.   But Glaxo's vaccine is adjuvant or additive, and the company claimed that its efficacy lasted longer.

Because of this, analysts anticipated a big hurdle for approval of Glaxo's vaccine.   The FDA is more caution about approving new adjuvants because of the potential risk of side effects, according to Reuters.