The strong association between vaccination with RRV-TV and intussusception among otherwise healthy infants supports the existence of a causal relation. Rotavirus vaccines with an improved safety profile are urgently needed.

Varicella disease has declined dramatically in surveillance areas with moderate vaccine coverage. Continued implementation of existing vaccine policies should lead to further reductions of varicella disease in these communities and throughout the United States.

Since 1990, the reported incidence of pertussis has increased in the United States with peaks occurring every 3-4 years. On the basis of analysis of pertussis cases reported to the Centers for Disease Control and Prevention, the incidence remained stable among children aged younger than 5 years, most of whom were protected by vaccination. In contrast to 1990-1993, during 1994-1996, the average incidence among persons aged 5-9 years, 10-19 years, and 20 years or older increased 40%, 106%, and 93%, respectively. Since 1990, 14 states reported pertussis incidences of > or =2 cases per 100,000 population during at least 4 years between 1990 and 1996; seven of these states also reported that a high proportion of cases occurred in persons aged 10 years or older. Analysis of national data on pertussis did not provide sufficient information to fully elucidate the relative importance of multiple possible explanations for the increase in the incidence of pertussis in adolescents and adults. Improvement in diagnosis and reporting of pertussis in this age group, particularly in some states, is an important factor contributing to the overall increase.

Historically, varicella has been a disease predominantly affecting preschool and school-aged children in the United States. The live attenuated varicella vaccine was licensed in this country in 1995 and has been recommended for routine use in immunization of children 12 to 18 months of age. As an increasing proportion of the children in the United States are protected from varicella by vaccination, changes in the current epidemiology of the disease are anticipated. This article reviews the current epidemiology of VZV infection and outlines issues related to possible changes in varicella epidemiology that may follow widespread use of the live varicella (Oka) vaccine.