Precancerous cervical lesions are on the decline among young women in Connecticut, the first indication nationally that a vaccine for human papillomavirus (HPV) types 16 and 18 may be working. Researchers led by Dr. Linda M. Niccolai, an associate professor at the Yale School of Public Health, used a statewide surveillance registry to examine the incidence of high-grade cervical lesions in women ranging from 21 to 39 years old. Cervical and other types of genital and oropharyngeal cancers are known to be caused by HPV. A vaccine to fight HPV infections was introduced in 2006. Use of the vaccine has risen sharply to include 61 percent of the state’s adolescent female population who had received at least one dose of the three-dose regimen. The six-member research team found that the incidence of precancerous lesions fell from 834 per 100,000 in 2008 to 688 by 2011 in the 21- to 24-year-old age group. The findings are consistent with the results of studies conducted in Australia and Europe.