Are chickenpox parties history?
A decade after the debut of the varicella vaccine, chickenpox is fading away, wrote Jeremy Manier in today's Chicago Tribune.
While the story noted that the U.S. Centers for Disease Control now recommends two chickenpox shots instead of one, Manier didn't have space to explain what researchers have long known: The varicella vaccine is effective, but immunity often doesn't last until adulthood.
Chickenpox is a much more serious disease in adults and pregnant women than in children. But the only way to know how attenuating chickenpox in early childhood will affect adults is to vaccinate and then wait 20 years.
Now that we're about halfway there, we've seen studies that show the vaccine's effectiveness decreases significantly after 1 year, although most cases of breakthrough disease are mild, according to this 2004 study in the Journal of the American Medical Association.
"If administered at younger than 15 months, the vaccine's effectiveness was lower in the first year after vaccination, but the difference in effectiveness was not statistically significant for subsequent years,” the study authors noted.
The problem is that with fewer natural cases of the disease, unvaccinated children or those whose first dose of the vaccine fails to work are getting chickenpox later in life, when the risk of complications is higher, according to a 2007 study in the New England Journal of Medicine.
"There's a 20 times greater risk of dying compared to a child, and a 10 to 15 times greater chance of getting hospitalized," said Dr. Jane Seward of the CDC, who worked on the NEJM study.
Chickenpox can be life-threatening to children with crippled immune systems. In healthy kids, it's often nothing more than itchy red bumps.
In fact, one reason Merck initially decided to market the chickenpox vaccine was that it said there was a demand from working parents who were inconvenienced when their children get the disease. (Parents also didn't want their kids to end up with scars from the chickenpox.) Lost wages accounted for 95 percent of the cost of the disease, according to the CDC.
Still, Manier says Seward's quote alone misses another point: that the rates of hospitalization and death have declined for all age groups because of the vaccine.
In addition, Manier added, the authors of the Pediatrics study that found chickenpox has virtually disappeared from many parts of the country also noted: "The median age at infection increased for both vaccinated and unvaccinated individuals, although incidence rates for all age groups were lower."
That means, Manier said, that "of all the children who get sick, more are now older. But those older kids still get sick at a lower overall rate than they did before. They account for a bigger slice of the pie, but the pie itself is way smaller than it used to be."