SINGLE CHICKENPOX SHOT MAY NOT BE ENOUGH

by Jim Ritter - Health Reporter
Chicago Sun Times
February 18, 2004

The chickenpox vaccine loses effectiveness over time, raising the possibility kids will need a booster shot, researchers reported Tuesday.

That would bring the number of required vaccine shots in Illinois to 20.

The vaccine was 97 percent effective one year after the shot and 84 percent effective at eight years, according to the study in the Journal of the American Medical Association.

Other vaccines also lose immunity, so the finding wasn't surprising. Moreover, most vaccinated kids who do get sick have "very mild" cases, said lead author Dr. Marietta Vazquez of Yale University. "The vaccine works very well."

The chickenpox shot is recommended for children 12 months to 18 months old. The study found that kids immunized after 15 months were less likely to experience waning immunity.

Chickenpox symptoms include fever, fatigue and a rash that usually begins as small red spots. It can be mild (fewer than 50 spots), moderate (50 to 500 spots) or severe (more than 500 spots). The vaccine is nearly 100 percent effective in preventing moderate and severe cases, said a spokesman for Merck & Co., the vaccine manufacturer.

But a 2002 study in the New England Journal of Medicine illustrates the vaccine isn't foolproof. At a New Hampshire day-care center, a boy who had been vaccinated three years earlier got chickenpox and transmitted it to 15 other kids, most of whom had been vaccinated.

The vaccine was approved in 1995 and now is required for schoolchildren in 42 states, including Illinois.

Before the vaccine, chickenpox caused an estimated 100 deaths and 10,000 hospitalizations per year. But for most kids, the disease isn't serious.

Some experts and parents say the vaccine should be voluntary. They argue that kids might be better off getting the disease when they're young, thereby obtaining lifelong immunity. Chickenpox can be severe in adults, and it's unknown how much protection a single shot will provide when kids grow up, they say.

The vaccine costs about $55, plus the cost of giving the shot. Studies have found it's worth the cost because working parents don't have to miss work to care for infected children. But the vaccine might not be cost-effective if a booster shot were needed, critics say.

To reduce the number of shots, Merck is developing a shot that combines the chickenpox and measles-mumps-rubella vaccines into a single shot.

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Merck & Co. Inc. combination vaccine PROQUAD(R) (Measles, Mumps, Rubella and Varicella (Oka/Merck) Virus Vaccine Live)