The Advisory Committee on Immunization Practices (ACIP) has updated recommendations for the use of varicella (chickenpox) vaccine. The updated recommendations, published in the May 28, 1999 issue of the reports and recommendations series of Morbidity and Mortality Weekly Report, establish child care and school entry requirements for varicella vaccine, recommend use of the vaccine following exposure and for outbreak control, recommend use of the vaccine for some children infected with the human immunodeficiency virus (HIV), and recommend vaccination of adults and adolescents at high risk for exposure. The report also contains discussions on reporting postlicensure adverse events, development of herpes zoster and transmission of vaccine virus. The following information has been taken from the ACIP report:

• ACIP recommends that all states require children who will be entering day care facilities and elementary schools either receive varicella vaccine or have other reliable evidence of immunity to varicella. Other evidence of immunity is defined by ACIP as a physician's diagnosis of varicella, a reliable history of the disease or serologic evidence of immunity. It is also recommended that states consider having a policy that requires evidence of varicella vaccination or other evidence of immunity for children entering middle school.

• ACIP now recommends that the vaccine be given to susceptible persons following exposure to varicella. If the exposure does not cause varicella infection, the postexposure vaccination should protect against subsequent exposure. Although postexposure use could apply to hospital settings, ACIP recommends routine vaccination of all susceptible health care workers and vaccination is the preferred method for preventing varicella in a health care setting.

• State and local health departments should consider using varicella vaccine for outbreak control either by advising exposed susceptible persons to receive the vaccination from their physician or by offering vaccination through the health department. The National Immunization Program of the Centers for Disease Control and Prevention (CDC) does provide guidelines for varicella outbreak investigation and control.

• ACIP has designated susceptible persons aged 13 years and older who live in households with children as a new high-risk group who need to receive the varicella vaccine. The other high-risk groups include (a) persons who live or work in environments where transmission of varicella zoster virus is likely; (b) persons who live and work in environments where transmission can occur; (c) nonpregnant women of childbearing age; and (d) international travelers.

• ACIP has also recommended that the vaccine be made available to children with humoral immunodeficiencies and selected children with HIV infection (i.e., in CDC Class N1 or A1, with age-specific CD4 T-lymphocyte percentages of 25 percent or more). The recommendations regarding use of varicella vaccine in persons with other conditions associated with altered immunity (e.g., immunosuppressive therapy) or in persons receiving steroid therapy have not changed.

Adverse Events

The Vaccine Adverse Event Reporting System (VAERS) can provide data on potential adverse events. The CDC reports that during March 1995 through July 1998, a total of 9.7 million doses of varicella vaccine were distributed in the United States. VAERS received 6,580 reports of adverse events; 4 percent of these events were serious. Most of the reports were in children under 10 years. The most frequently reported adverse event was rash.

While transmission of the vaccine virus is rare, the CDC has documented three occasions of transmission (out of 15 million doses of varicella vaccine). All three cases resulted in mild disease without complications, according to ACIP. Secondary transmission has not been documented in the absence of a vesicular rash after vaccination.