In the five years before the vaccine, chickenpox caused or contributed to an average of 145 deaths each year. That dropped to 66 in just a few years, researchers at the Centers for Disease Control and Prevention reported in Thursday's New England Journal of Medicine.
The death rate was slashed by as much as 92 percent in the 1-to-4-year-old group.
"It's really a very dramatic success story for the vaccination program," said Jane F. Seward, one of the CDC researchers.
Until the vaccine became available, nearly everyone got a case of chickenpox, which is highly contagious. Healthy children and adults can die from complications that include viral pneumonia, infection of the brain and bleeding.
Now, with 85 percent of young children in the United States getting a vaccine shot, chickenpox cases have dropped from 4 million a year to 800,000.
The researchers reviewed death certificates from 1990 through 2001 and found that chickenpox deaths went down as the use of the vaccine increased. The death rate did not drop for those over 50, but the researchers said those deaths were more likely due to shingles, which is caused by dormant chickenpox virus and results in a painful rash and nerve pain.
The vaccine is considered about 80 percent effective, and vaccinated children can still get a mild case.
Dr. Marietta Vazquez of the Yale School of Medicine said a second dose of vaccine may be needed to boost children's immunity, citing outbreaks at day-care centers and schools where most children were vaccinated.
Seward said a second chickenpox shot is under discussion.