How will use of varicella vaccine affect the epidemiology the disease?
As all vaccines have done, varicella vaccine will affect the epidemiology of the disease. Most importantly, the incidence of disease will decline in all age groups. This is already occurring in sites conducting active surveillance for varicella. In 1999, there was a dramatic decline in cases and the expected spring time increase in varicella cases did not occur. As we would expect, the greatest decline in incidence has occurred among children 1-4 years; however, the decline in incidence is occurring in all age groups, including adults who currently do not have recommendations for varicella vaccine and infants < 12 months who are not eligible for vaccination. As transmission continues to decline, decreasing circulation of wild virus will increase the likelihood that unexposed and unvaccinated children will enter adolescence and adulthood without immunity. Thus, it is increasingly important to offer vaccine to all susceptible adolescents and adults as well as children in line with curren
