There's a new flu vaccine option this year, and the federal government has placed a large order with GlaxoSmithKlinePLC, which has a big footprint across the Philadelphia region.

In six of the last 11 years, scientists have guessed wrong about the best formula to fight off the seasonal flu, said pediatrician Dr. Leonard Friedland, who leads scientific affairs and public policy at GlaxoSmithKline Vaccines in North America.

Four common strains of flu virus cause the sniffling and body aches that come with flu season each year, but for three decades, medicine's best defense against the flu has been a vaccine that fights just three strains of virus.

So every year, long before the first sneeze, world health experts work to design the best formula. The traditional three-strain—or trivalent—vaccine includes a defense against two sub-class A influenza strains and one of two B strains. Scientists make their best guess about which B strain will be most dominant in the upcoming season.

When the scientists get it wrong, that's called a mismatch. The trivalent vaccine does fight the flu, but when there's a mismatch, the protection the shot offers isn't quite as good as doctors would like.

The new weapon in the arsenal is supposed to erase worries about a mismatch.

MedImmune, GlaxoSmithKline and Sanofi Pasteur now are approved to sell a four-strain flu vaccine.

GSK's brands are Flulaval Quadrivalent and Fluarix Quadrivalent. Friedland said he expects GSK to be the biggest supplier of the new vaccine to the Centers for Disease Control and Prevention. The company, which has research and development operations in the Philadelphia region, employs about 5,000 workers in the area.

The drugmakers are betting that their four-strain vaccines will improve the chances that the immunization is effective.

"The CDC is not recommending that one group of patients receive a four-strain vaccine while another group receive a three-strain," Friedland said. "What (the CDC is) recommending is that everybody who is eligible be vaccinated for influenza, and that health care providers use the vaccine that they can get available for their practice."

Main Line Health in the Philadelphia suburbs is stocking some of the new vaccine for patients, and Connie Cutler, who leads infection prevention at the five-hospital health care network, said she purchased the shots especially for her medical and health-care staff.

"We made the decision, that despite the additional cost cause, it would be beneficial to us to purchase the quadrivalent vaccine," Cutler said. "We are taking care of newborns, we're taking care of cancer patients, and we want to make sure that we have a high level of protection as possible."

Cutler said GSK's four-strain vaccine costs Main Line about $5 more per shot compared with the three-strain version.