Shingles cases have dropped sharply among younger American adults, and researchers say the childhood chickenpox vaccine is the likely reason. The findings come from a major study by Epic Research published on October 2.

The team analysed electronic health records of more than 85 million adults. The sharpest fall was between people born from 1991 to 1995 and those born from 1996 to 2000. About 46 out of every 10,000 people in the older group were diagnosed with shingles. In the younger group, it was just 17 out of every 10,000. That is a 62 percent drop.

The younger group is the first generation that could get the routine childhood chickenpox vaccine, which the United States introduced in 1995. Shingles is caused by the same virus as chickenpox. The virus can hide in nerves and reactivate years later.

“This is the pattern we would expect if childhood chickenpox vaccination lowers the risk of developing shingles later in life,” said study author Kersten Bartelt. The researchers noted they did not check individual vaccination records. Older adults still face the highest risk of shingles.