Strategies to Prevent Varicella among Newly Arrived Adult Immigrants and Refugees: A Cost-Effectiveness Analysis

In temperate, industrialized countries, such as Canada, varicella is a common disease in childhood [1].In tropical countries, for reasons that are not entirely clear, varicella occurs among young adults.Seroprevalence data from tropical regions suggest that up to 30% of individuals are susceptible to varicella at 20 years of age, and 5%-10% remain susceptible at 30 years of age [2, 3].There have been many reported outbreaks of varicella in immigrant populations in industrialized countries, suggesting that foreign-born adults are disproportionately susceptible [4][5][6].Recent immigrants also have a high risk of exposure, because many are the parents of young children, who have a high annual incidence of varicella unless they are vaccinated.Varicella is more severe in adults than in children and is associated with a greater risk of complications and death [7].The fetuses and neonates of pregnant women who develop varicella may develop congenital or neonatal varicella, with high case-fatality rates [8,9].Preventing varicella in young adult immigrants, therefore, is important because of the susceptibility of this population and the potential for adverse outcomes.A live-attenuated vaccine was licensed in Canada in 1998 and is now universally available for children !13