U.S. deaths from chicken pox plummeted to a record low after a national vaccination program to prevent the disease was introduced in 1995, a study suggests.

The findings may prompt calls for a similar program in Canada, where three provinces and a territory still require parents to pay for the vaccine out of pocket.

In the five years before the vaccination program began in the United States, the childhood disease caused or contributed to about 145 deaths each year.

Chicken pox deaths among young American children have dropped by as much as 92 per cent.
Chicken pox deaths among young American children have dropped by as much as 92 per cent.

That dropped to 66 in just a few years, researchers from the U.S. Centres for Disease Control and Prevention report in the Feb. 3 issue of the New England Journal of Medicine.

Among children ages one to four, the death rate from chicken pox, or varicella, decreased by as much as 92 per cent.

"It's really a very dramatic success story for the vaccination program," said Jane Seward, one of the researchers.

U.S. cases drop from 4M to 800,000

Until the vaccine was introduced, almost everyone caught the disease, which is highly contagious. It usually only causes minor scars, but can kill through complications that include viral pneumonia, brain infection and flesh-eating disease.

The CDC researchers, who reviewed death certificates from 1990 through 2001, found that chicken pox cases in the United States have dropped to 800,000 a year from four million.

About 85 per cent of young American children receive the vaccine, which wards off the illness in about four out of five people.

Studies indicate the vaccine's effectiveness wanes slightly over time and mild outbreaks of chicken pox have been reported in schools and day care centres where most children have been immunized.

The CDC study's lead authors – Yale University pediatricians Marietta Vazquez and Eugene Shapiro – suggest in a related article that it may be worth giving children a second dose of the vaccine.

A previous study found that the U.S. rate of hospitalization for chicken pox dropped 74 per cent in the first six years after the vaccine went on the market.

That saved $130 million Cdn in hospital costs alone each year – enough to cover most of the costs of the vaccination program, the researchers said.

Only 1 in 5 Canadian toddlers vaccinated

In Canada, the annual cost of hospitalizing patients for chicken pox is an estimated $11 million. Health Canada estimates that the total cost to the economy, including lost productivity, tops $122 million.

The most recent figures show 20 per cent of toddlers get the vaccine, which was licensed for use in Canada in 1998.

While some provinces and territories offer free chicken pox immunizations, others require parents to pay for the vaccine out of pocket.