A shot in the arm for vaccines

They are lethal bacteria. They slink into the human body cloaked in any of 91 versions of fuzzy sugar clouds that act as a coat of armor as they assault the immune system.

For drug giant Wyeth, the opportunity to prevent these bacteria, known as pneumococci, from causing meningitis in children already rings up $2.7 billion in yearly sales of its Prevnar vaccine.

That figure could grow to $6 billion or $7 billion, according to some analysts' estimates, if the U.S. Food and Drug Administration approves a new version of the vaccine for use in children and, after that, in adults 50 and older.

Wyeth isn't the only big pharmaceutical company betting its future on a vaccine. Drug companies once viewed vaccine profits as poor relatives to blockbuster pills such as Pfizer Inc.'s Lipitor and AstraZeneca P.L.C.'s Nexium. Many vaccines are so crucial to preventing disease that drug companies can't charge high margins on them.

But the profit outlook for vaccines has shifted. Vaccines are more costly and challenging to manufacture than most other pharmaceuticals, and are almost invulnerable to generic competition. Overall drug sales grew only 8 percent in recent years, compared with 32 percent growth for vaccines, according to research firm Datamonitor.

Pneumococcal vaccines are especially challenging to create, because there are 91 strains of the bacteria. An effective vaccine must learn to recognize bacteria that don't always look the same.

So as Wyeth, whose U.S. pharmaceutical headquarters are in Collegeville, heads toward its year-end merger with Pfizer, of New York, investors' eyes are on Prevnar. Wyeth's current version of the vaccine protects against seven of the pneumococcal bacteria strains. Since Prevnar was introduced in 2000, rates of pneumococcal meningitis, an inflammation of the membranes around the brain caused by bacteria, have fallen 64 percent in children under age 2, according to a study published in January in the New England Journal of Medicine.

The drop in serious childhood infections paid off for adults, too, whose rates of pneumococcal meningitis fell 30 percent, the study said. Even though adults did not get the vaccination, lower rates of childhood diseases meant fewer infections in adults, an effect known as "herd immunity."

But the study also pointed to a troubling trend: Strains of pneumococcal bacteria not covered by Prevnar have grown more common, especially a type known as 19A, which is antibiotic-resistant and causes many of the infections in the United States.

Late last month, Wyeth asked the FDA to approve Prevnar 13, which protects against six additional types of pneumococcal diseases, including 19A, for use in infants and toddlers. The FDA granted the application fast-track status, a speeded-up process aimed at getting drugs that are effective against serious illnesses to market faster. Next year, Wyeth plans to apply for approval for Prevnar 13 for adults.

Every year, an estimated 915,000 people 65 and older get pneumonia, and 40 percent of them end up in hospitals, according to a 2004 paper in the journal Clinical Infectious Diseases. Pneumonia often kills older people, said Richard Stefanacci, a geriatrician at the University of the Sciences in Philadelphia.

The Centers for Disease Control and Prevention recommends that children younger than 2 and adults older than 65 get vaccinated against pneumococcal diseases. The current version of Prevnar is used in children, but the pneumococcal vaccine for adults is Merck & Co. Inc.'s Pneumovax 23.

Pneumovax protects against the most aggressive strains of the disease in adults, said Cynthia Whitney, chief of the CDC's respiratory-diseases branch. But the hope is that Prevnar 13 would protect against a wider spectrum of the disease because even milder versions can result in hospitalizations and long recoveries for the elderly.

Prevnar operates differently from Pneumovax. Besides increasing antibodies to fight pneumococcal bacteria, as Pneumovax does, Prevnar helps the immune system continue to recognize the bacteria long after the initial vaccination.

"The advantage of that is you not only produce better immune response but you produce a memory," said Peter Paradiso, vice president of scientific affairs at Wyeth Vaccines. In theory, that should give people who get Prevnar longer protection than Pneumovax provides. Some research suggests the benefits of Pneumovax decline significantly after five years.

But the scientific community is still waiting for Wyeth to complete studies of Prevnar's efficacy in adults. The company is conducting several studies of Prevnar 13 in adults, including one in Europe that will test it on about 80,000 people.

"There are a lot of theoretical benefits, but we just don't have a lot of data to show those effects," the CDC's Whitney said.