Varicella epidemiology has been changing since two doses of varicella vaccine were routinely recommended in the United States in 2006.

A recent study conducted in neighborhoods in Los Angeles County and Philadelphia reports significant declines in varicella during the first five years of the two-dose era (

, et al
). Varicella incidence (reported cases per 1,000 population) from 2006-’10 compared with 2002-’05 declined 76% in the Los Angeles neighborhood and 67% in the Philadelphia neighborhood. The declines were greatest among elementary school-aged children, the age group recommended to receive a second dose. However, declines occurred in all age groups, including infants and adults.

Over the same time period, varicella-related hospitalizations declined by more than 40%, and varicella outbreaks declined by 75%. The Philadelphia site reported no outbreaks after the two-dose policy was implemented. The Los Angeles site reported 12 outbreaks...

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