UPDATE 2-Wyeth says FDA extends Prevnar 13 review by 3 mos

* Says delay needed for FDA to review requested info

* Says FDA studying data on vaccine's physical properties (Adds details on new and original forms of Prevnar, byline)

By Ransdell Pierson

NEW YORK, Aug 11 (Reuters) - Wyeth WYE.N said on Tuesday that U.S. regulators will take three months longer than expected to review Prevnar 13, a more-protective new formulation of its Prevnar vaccine used to prevent pneumococcal disease in infants and toddlers.

Prevnar 13 is the most important product in Wyeth's pipeline of experimental drugs and vaccines. It also is being studied for potential use in adults, a new indication that could accelerate already booming sales of the Prevnar franchise.

Wyeth, which is expected to be acquired by Pfizer Inc (PFE.N) later this year, in late March submitted its marketing application for Prevnar 13 to the U.S. Food and Drug Administration.

The FDA in May granted the vaccine priority review status, meaning the agency would aim to complete its analysis of the application within six months, rather than within the standard 10-month review period.

But Wyeth on Tuesday said the FDA had informed it the review had been extended to Dec. 30, representing a three-month delay from the earlier planned action date of Sept. 30.

Wyeth said the delay was related to the company's submission to the FDA in late July of additional information about the new vaccine requested by the agency. The information involves analytical method validation and specification information relating to physical and chemical properties of the vaccine, Wyeth said in a release.

Prevnar 13 is designed to protect against 13 serotypes, or forms, of a bacterium called streptococcus pneumoniae (pneumococcus) that can cause an array of diseases, ranging from ear infections to pneumonia and meningitis.

Prevnar, which was introduced in 2000 and has annual sales of more than $3 billion, currently protects against seven serotypes that account for about 80 percent of potential infections. Wyeth has said the new product could broaden protection against perhaps 92 percent of potential infections in infants and toddlers.

Wyeth expects to seek regulatory approvals in 2010 to market Prevnar 13 to adults. Pneumonia caused by the pneumococcal organism is one of the biggest causes of death in older individuals and its incidence begins to increase when one is about 50 years old, and increases rapidly thereafter as the immune system weakens.

Shares of Wyeth were little changed in after-hours trading, while shares of Pfizer were unchanged. (Reporting by Ransdell Pierson; editing by Carol Bishopric, Bernard Orr)