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Volume: 25S5 - August 1999 Proceedings of the National Varicella Consensus Conference Varicella Vaccine Use in Special PopulationsEmphasis was placed on all susceptible healthy adults as the main target for varicella vaccination. However, a number of populations were identified for active targeting, including health care workers and household contacts of immunocompromised individuals. Recommendations regarding vaccination of health care workers refer both to occupational exposure to VZV and to the possibility that health care workers might transmit the virus to patients (see definition of health care workers in the General Recommendation). The principle that health care workers must be immunized against those diseases that they are capable of transmitting to individuals was considered to be important, reasonable, and realistic. Nonetheless, this was also recognized as a potential area of controversy. There was debate on the management of vaccinated health care workers exposed to wild type VZV. It was noted that in up to 20% of immunized adults exposed to varicella a breakthrough rash may develop. Regardless of age, a history of varicella is a highly reliable and valid way to determine an individual's immune status to varicella(1). Screening for the specified high-priority populations should be a two-step process, beginning with enquiry about a history of varicella and followed by serologic tests only for persons who have an uncertain or a negative history. Ideally, serologic tests to determine the need for immunization should be conducted only when they are considered to be cost-beneficial. Once high vaccination coverage rates have been achieved and maintained, controlling potential pockets of infection will be the key to controlling the disease, and outbreak intervention programs will become more important. During this control phase, the need for early detection of varicella cases among special population groups at high risk of infection may warrant more intense screening for immunization. Such groups may include immigrants (adults and children) and individuals in institutions such as penal institutions (where the closed setting, ease of transmission, and high percentage of high-risk populations such as HIV-positive individuals increase the risk of infection). History taking may be adequate, but information on immigrant seroprevalence was identified as a research need. In health care settings, post-exposure prophylaxis should be considered within 72 hours and up to 5 days after exposure for non-pregnant, susceptible staff and for susceptible inpatients, in consultation with infectious disease experts. However, post-exposure prophylaxis should not be substituted for immunization programs. In the control phase, post-exposure prophylaxis may need to be considered for the special situations or groups that follow: for susceptible persons following varicella exposure within 72 hours and up to 5 days of a point source exposure in daycare centres, in household settings, and in homeless shelters where there are lots of children. It is recommended that all susceptible persons be vaccinated at the same time. Providers in travel clinics may remind susceptible persons of the availability of the varicella vaccine, although there is no increased risk of acquiring the disease through travel. Recommendation 3.1 All healthy, susceptible non-pregnant adults should be targeted for vaccination. However, priority for active targeting should be given to health care workers; household contacts of immunocompromised individuals; child care workers; and primary and secondary school teachers. Recommendation 3.2 Active targeting plan: All jurisdictions and employers with an existing responsibility (such as Occupational Health, Public Health, obstetric care workers, primary care physicians, etc.) are to direct campaigns of screening (history of varicella with or without serology) and offer vaccine to the active targets. Health care workers Recommendation 3.3 Susceptible health care workers should be immune prior to employment or should be immunized according to a two-dose schedule to be completed within 2 months, to minimize outbreaks and loss of time due to varicella in health care settings. All susceptible health care workers currently in the system should be immunized. Initial priority should be given to immunizing health care workers on wards or in patient care settings that contain susceptible high-risk patients (e.g. settings with immunocompromised patients, intensive care units, and emergency rooms). Recommendation 3.4 Identifying susceptibles: Before an employee begins employment, a varicella history should be obtained. If there is any doubt about previous disease or vaccination, or the history is negative or unknown, serologic testing should be performed. If the result is negative, the employee should be immunized. If the individual receives the vaccine, (s)he should be furloughed or reassigned only if there is a varicella-like rash. Recommendation 3.5 Post-exposure management: Significant exposure for health care workers should be defined as 15 minutes face-to-face or 1 hour in a patient room. Immunized and exposed health care workers whose antibody status is not known should be watched vigilantly for a varicella-like rash, with or without serologic testing. If a health care worker has a rash, it should be reported to occupational health. The worker should be granted furlough or reassigned for the duration of the rash. Immunocompromised individuals Recommendation 3.6 Live, attenuated vaccine should not be routinely given for immunocompromising diseases (e.g. lymphoma, congenital or acquired immunodeficiency) or treatments associated with T-cell abnormalities (e.g. intensive chemotherapy, high dose steroids, cyclosporine, azathioprine, methotrexate, tacrolimus). Recommendation 3.7 Immunization should be discussed with an infectious disease expert in the following cases:
Recommendation 3.8 The following persons may be safely immunized:
Screening of susceptible persons Recommendation 3.9 Prior to vaccination, screening (history with/without serology) is recommended for the following special groups: health care workers, teachers, daycare staff, and persons in institutions of health education (e.g. nursing schools, medical schools). A reliable history of varicella is satisfactory to establish immunity. If there is no known history or the history is uncertain, serology should be performed. Recommendation 3.10 Obstetric care providers should identify the varicella status of women during pregnancy, and immunize postpartum those who are susceptible prior to discharge. Varicella screening should be added to obstetric prenatal chart/laboratory requisitions to be checked separately for potential identification of susceptible women. Primary care providers should identify the varicella status of women of reproductive age and immunize them if necessary.
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