Before 1995, when the varicella vaccine came into widespread use, chickenpox affected about 90 percent of the population, leading to thousands of hospitalizations and about 100 deaths a year.
"Now a very safe vaccine will totally prevent it from happening," said the lead author, Dr. Roger Baxter, co-director of the Kaiser Permanente Vaccine Study Center in Oakland, Calif.
Between June and November 1995, researchers began studying 7,585 children vaccinated between the ages of 1 and 2. They interviewed their parents every six months, asking about the occurrence of both chickenpox and shingles, the painful rash that can occur after recovery from chickenpox. In June 2006, a second vaccine dose was recommended, and the researchers followed those cases through the end of the study in 2009.
The analysis, published online in Pediatrics, found 1,505 cases of chickenpox, all except 30 of which were mild or moderate, involving less than 300 lesions. There were no cases among children who received a second dose.
Image: Infant getting vaccine, via Shutterstock