UPDATE 2-US panel backs Pfizer's newer Prevnar vaccine

* FDA panel: Pfizer’s Prevnar 13 safe, effective

* FDA decision due by late December

* Pfizer shares gain 1.4 pct (Recasts; Adds panel member quotes)

BETHESDA, Md., Nov 18 (Reuters) - Pfizer Inc PFE.N won a key endorsement on Wednesday for a new version of a blockbuster vaccine that fights pneumonia, meningitis and other diseases caused by pneumococcus bacteria.

A Food and Drug Administration advisory committee voted 10-1 the Prevnar 13 vaccine was safe and effective for infants and toddlers. The vaccine is the most important experimental product the company acquired in its recent purchase of Wyeth.

The FDA usually approves products that win support from advisory panels. A decision on Prevnar 13 is due by Dec. 30.

The vaccine is designed to fight 13 forms of a bacterium called streptococcus pneumoniae, or pneumococcus.

The original Prevnar, which targets seven strains, was introduced in 2000 and has annual sales around $3 billion.

Pfizer’s recent $67-billion purchase of Wyeth helped the the world’s largest drugmaker diversify in the areas of vaccines and injectable biotechnology medicines.

Company officials who argued in favor of Prevnar 13 to the FDA panel said the incidence of pneumococcal disease in children under five had dropped sharply after the introduction of the original vaccine.

They estimated the added protection from Prevnar 13 could reduce deaths from pneumococcus by an extra 9,800 over 10 years. The new vaccine targets a strain called 19A that has emerged as the most common cause of pneumococcal infection in the United States.

“We’re very gratified to have achieved a positive recommendation,” Dr. Emilio Emini, Pfizer’s chief scientific officer for vaccine research, said after the panel ruling.

FDA reviewers said some measurements used in a Pfizer study failed to show the vaccine was equivalent to the original Prevnar for three of the strains. Panel members said they felt confident Prevnar 13 would be effective based on levels of infection-fighting antibodies that were seen.

Pamela McInnes, a researcher at the National Institutes of Health, said there were “quite compelling data in terms of functional antibodies. I’m very persuaded by that.”

Potential side effects were similar with Prevnar 13 and the original shot and included tenderness at the injection site and irritability. Both vaccines require a total of four injections given at two, four, six and 12 to 15 months.

Vicky Debold, the panel’s consumer representative and sole vote against Prevnar 13, questioned if the risks were fully understood as potential side effects were compared with the original Prevnar.

“I’m having a really hard time understanding how we can understand safety comparing Prevnar 13 to Prevnar,” said Debold, director of patient safety at the National Vaccine Information Center.

Prevnar 13 also is being studied for potential use in adults, a new use that could accelerate already booming sales of the franchise.

Pneumonia caused by the pneumococcal organism is one of the biggest causes of death in older people and its incidence begins to increase after age 50.

GlaxoSmithKline Plc GSK.L has a rival vaccine, called Synflorix, that is active against 10 strains. Synflorix is approved in Europe and some other markets, but not the United States.

Merck MRK.N also sells the Pneumovax 23 vaccine, which fights 23 types of pneumococcus and is the only vaccine of its type that is FDA-approved for adults.

Pfizer shares gained 1.4 percent to close at $18.19 on the New York Stock Exchange. (Reporting by Lisa Richwine; Editing by Tim Dobbyn, Bernard Orr)