The chickenpox vaccine was able to reduce the incidence of the disease by 90 percent, a new study released by the U.S. Centers for Disease and Prevention showed.

The study was released Tuesday in the journal Pediatrics.

“The U.S. varicella vaccination program has dramatically reduced varicella incidence and related complications, hospitalizations and deaths,” CDC researchers said.

But some infectious disease experts fear that too many parents may neglect to have their children vaccinated with chickenpox. Overall, chickenpox cases have fallen by 90 percent since the vaccine was introduced in 1995. But the fact that the vaccine has worked so well has led some parents to believe that chickenpox is no longer a health threat.

The study found that from 1995 to 2005 the chickenpox vaccine has been able to cut down on the number of hospitalization related to the disease by more than 75 percent. Child deaths from the disease, which had been at about 50 or 60 a year, became extremely rare.

A single shot of vaccine protects only 85 percent of children against the disease and it is not sufficient to stop the spread of the virus in public places, such as schools. The other children can get “breakthrough” varicella. On the other hand, experts say that no vaccine is 100 percent effective.

Two months ago, the U.S. CDC recommended that people aged 60 or older be vaccinated with Zostavax, which prevents shingles, a painful disorder related to chickenpox. After a person has had chickenpox, the virus remains in his body and it can later reactivate as shingles. The CDC said that for people ages 60 to 69, the vaccine cuts the occurrence of the disease by 64 percent.