INFECTION CONTROL NEWSLETTER

Broad Street Solutions
James Marx, RN, MS, CIC Editor
P.O. Box 16557
San Diego, CA 92176
(619)563-0274 Voice/FAX
jmarx@concentric.net

Due to the increasing demands for newsletter subscriptions, a fee for this newsletter will begin in January 1998. This fee will only apply to subscribers who are not currently clients of Broad Street Solutions. The annual subscription fee of $24.00 will begin with January 1998 issue. Participants of the Infection Control School for Long Term Care Nurses can receive the first year's subsciption for half the annual fee if they subscribe during the class. A subscription form will be available beginning in October 1997.

VARICELLA VACCINATION PROGRAM: PART II

All susceptible health-care workers should ensure that they are immune to varicella. In health-care institutions, serologic screening of personnel who have a negative or uncertain history of varicella is likely to be cost effective. Routine testing for varicella immunity after two doses of vaccine is not necessary for the management of vaccinated health-care workers who may be exposed to varicella, because 99% of persons are seropositive after the second dose. Seroconversion, however, does not always result in full protection against disease. More information is needed concerning the risk for transmission of vaccine virus from vaccinees in whom varicella-like rash develops following vaccination. On the basis of available data, the risk appears to be minimal, and the benefits of vaccinating susceptible health-care workers outweigh this potential risk. As a safeguard, institutions may wish to consider precautions for personnel in whom rash develops following vaccination and for other vaccinated personnel who will have contact with susceptible persons at high risk for serious complications. Vaccination should be considered for unvaccinated health-care workers who are exposed to varicella and whose immunity is not documented. However, because the protective effects of postexposure vaccination are unknown, persons vaccinated after an exposure should be managed in the manner recommended for unvaccinated persons.

Vaccination is recommended for susceptible persons who have close contact with persons at high risk for serious complications (e.g., health-care workers and family contacts of immunocompromised persons). Vaccination should be considered for susceptible persons in the following groups who are at high risk for exposure:

• Persons who live or work in environments in which transmission of VZV is likely (e.g., teachers of young children, day-care employees, and residents and staff in institutional settings).
• Persons who live or work in environments in which varicella transmission can occur (e.g., college students, inmates and staff of correctional institu-tions, and military personnel).
• Nonpregnant women of childbearing age. Vaccination of women who are not pregnantăbut who may become pregnant in the futureăwill reduce the risk for VZV transmission to the fetus.

Varicella immunity may be ascertained at any routine health-care visit or in any setting in which vaccination history may be reviewed, such as the pre-employment physical. Women should be asked if they are pregnant and advised to avoid pregnancy for 1 month following each dose of vaccine.

Approximately 15% of the population will experience herpes zoster (shingles) during their lifetime.

VARICELLA ANTIBODY TESTING

A reliable history of varicella is a valid measure of immunity. Because the rash is distinctive and subclinical cases rarely occur, most parents know if their child has had varicella. A negative history of varicella substantiated by a parent may be more accurate than a self-reported negative history given by an adult. Serologic tests have been used to assess the accuracy of reported histories of varicella. In adults, a positive history of varicella is highly predictive of serologic immunity (97%‚99% of persons are seropositive); however, the majority of adults who have negative or uncertain histories are also seropositive (71%‚93%). The appropriateness of a laboratory test to detect antibody to VZV depends on the purpose for obtaining the information; tests differ in their ability to detect antibody acquired from natural varicella versus antibody acquired from vaccinationălevels of which are lower than those following natural infection. Likewise, tests that rapidly assess the susceptibility of persons at high risk who are exposed to varicella differ from those used in serologic surveys. ELISA tests, which are commercially available, range in sensitivity from 86% to 97% and range in specificity from 82% to 99% in detecting antibody after natural varicella infection.

HANDLING AND STORAGE OF VACCINE

To maintain potency, the lyophilized vaccine must be stored frozen at an average temperature of <5 F (<-15 C). When tested, VARIVAX has remained stable in frost-free refrigerators. Refrigerators with ice co-partments that are either not tightly enclosed or enclosed with unsealed, uninsulated doors (e.g., small, dormitory-style refrigerators) may not meet temperature requirements. Regardless of the type of freezer, providers should check the adequacy of their freezer by verifying its temperature before obtaining vaccine. The diluent should be stored separately either at room temperature or in the refrigerator. The vaccine should be reconstituted according to the directions in the package insert and only with the diluent supplied with the vaccine, which does not contain preservative or other antiviral substances that could inactivate the vaccine virus. Once reconstituted, the vaccine should be used immediately to minimize loss of potency. The vaccine should be discarded if not used within 30 minutes after reconstitution.