Vaccines have long played a key role in pediatric medicine, and health authorities have also promoted flu and pneumonia shots for adults. But there have been few vaccines against other adult infectious diseases. Inoculations are both expensive to develop and hard to deliver to the elderly market, where reimbursement is spotty and patients aren't exactly pestering their doctors for yet another shot.
But the graying of populations throughout the industrialized world, combined with a better understanding of the aging immune system, makes adult vaccines a market worth pursuing. Such Big Pharma guns as Merck (MRK), Wyeth (WYE), GlaxoSmithKline (GSK), Sanofi-Aventis (SNY), and a handful of biotech startups are developing more than 30 vaccines for the elderly, including improved jabs against flu and pneumonia. Clinical trials are also under way for vaccines against hospital-acquired infections, respiratory viruses, and avian flu.
Merck is already proving the strength of the elderly market with Zostavax. It's the first vaccine against shingles, a painful rash set off by the same virus that causes chicken pox. Zostavax was approved in 2006 for adults 60 and over, and industry analysts expect sales to total $200 million next year. Although Zostavax is hardly a blockbuster, its success against a disease that's the bane of some 500,000 elderly people each year in the U.S. has given a glow to the adult vaccine sector. Glaxo is testing a second shingles vaccine, and market researcher Kalorama Information predicts that sales of all adult vaccines could rise to $7.5 billion by 2012, up from $3.7 billion in 2005.
Those numbers apply only if all these jabs get to their intended targets, however, and that is by no means a lock. A huge infrastructure exists to ensure that children get vaccinated--pediatricians long practiced in administering shots, laws requiring inoculations, and government guarantees of reimbursement. None of this is in place for aging patients. So even though a shot costing as little as $6 can cut the risk of death from influenza by 48%, according to just-published data, only 65% of senior citizens are vaccinated each year.
LEFT IN THE COLD
Elderly flu vaccination rates in the U.S. have held steady at that level for the past eight years, despite a federal goal to raise compliance to at least 85%. "Many internists who deal with adults don't even think of vaccination as part of their practice," says Jane Horvath, director of public policy at Merck. Adds Dr. Gregory A. Poland, head of vaccine research at the Mayo Clinic: "You always have a group who cannot be convinced the vaccine is safe and effective. An elderly person may not be able to make that extra trip to the doctor, and although Medicare pays for the flu shot, some private insurers don't."
Getting vaccines to work in the aged is no easy task, either. A flu vaccine that protects 90% of young adults and children is about half as effective in people 60 and over. And multipart vaccines for kids can peter out by age 60, leaving the elderly susceptible to childhood diseases they thought they'd escaped.
This depressing state of affairs stems from a relentless process called immunosenescence--in laymen's terms, the state you reach when your body's defenses are worn out by living. The immune system is centered in the thymus, which springs into action whenever viruses or bacteria invade, or defanged versions are introduced as vaccines. The thymus pumps out infection-fighting T-cells that ideally remain on guard for many years. But by 60, the thymus has lost much of its ability to manufacture T-cells, and the ones that have been circulating for decades often lack the strength to continue fighting.
It doesn't help that the thymus spends decades standing sentinel against a seemingly benign virus called cytomegalovirus (CMV), which infects up to 85% of all humans. CMV rarely causes disease, but it's so taxing to the immune system that some drugmakers are working on CMV vaccines.
Companies are also pursuing better adjuvants--materials that can boost a vaccine's potency. After 15 years of work, Glaxo says it has come up with a group of 25 new adjuvants that can be used in a broad range of vaccines. If such adjuvants work, virtually any harmful microbe could be an elderly vaccine target, says Dr. Dan L. Longo, scientific director of the National Institute on Aging. "The reward for developing an intervention you can give to an entire population is a very positive incentive, and drug companies are responding," he says.
Flu shots really work...
The evidence is in. Looking at data from tens of thousands of people 65 or older through 10 consecutive flu seasons, doctors at the Minneapolis Veterans Affairs Medical Center and several HMOs have linked vaccination with a 27% reduction in risk of hospitalization for pneumonia or influenza. Risk of death dropped by 48%. The results appear in the Oct. 4 issue of The New England Journal of Medicine.
...But still no AIDS vaccine
The latest blow came in September when Merck () pulled the plug on a three-year-old clinical trial because the vaccine simply didn't protect patients against HIV. In an Oct. 7 article, The Philadelphia Inquirer quoted Merck's head of vaccine research grimly saying it's unlikely any current approach will work.
By Catherine Arnst