Literature Reviews
Literature Reviews
Weber DJ, Rutala WA, Hamilton H. Prevention and control of varicella-zoster infections in healthcare facilities. Infect Control Hosp Epidemiol 1996; 17:694-705.
This article reviews nosocomial outbreaks associated with varicella-zoster virus (VZV) and provides detailed algorithms for pre-exposure immunization and post-exposure management of health care workers exposed to VZV.
The authors note that VZV causes both varicella and herpes zoster. Varicella can result in serious morbidity and mortality for adults, neonates, or immunocompromised patients. Mortality from herpes zoster for elderly people can be 3.7-fold higher than from varicella. For those reasons, the federal Centers for Disease Control and Prevention recommends that hospitals screen HCWs for VZV immunity and, if susceptible, provide the recently licensed vaccine unless contraindicated.
In clinical trials on adults, two doses of vaccine administered four to eight weeks apart induced a seroconversion rate of approximately 75% four weeks after the first dose and 99% four weeks after the second dose. Antibody levels persist at least one year in adults given two vaccine doses. Side effects of immunization in adults include fever, injection site complaints, a varicella-like rash at the injection site, and a generalized varicella-like rash.
Sixty percent to 80% of U.S. HCWs have had varicella. The authors note that a history of prior household exposure to VZV is not a reliable immunity indicator. Among HCWs with a negative or uncertain history of infection, reported serosusceptibility varies from 4% to 47%. Overall, HCWs’ susceptibility to varicella ranges from 1% to 7%. Two percent to 16% of susceptible workers have developed clinical varicella following nosocomial exposure to VZV infection.
Why immunize?
HCWs should be immune to VZV for three reasons: They could transmit infection to patients, they could acquire infection from patients, and the presence of susceptible staff results in significant costs for health care organizations. Costs are associated with removing staff from patient contact following exposures, administration of varicella-zoster immune globulin (VZIG) to immunocompromised patients exposed to workers with incubating or clinical varicella, and time and effort of hospital staff in evaluating exposures.
"Decision analysis has demonstrated that immunization of health care workers susceptible to varicella is cost-effective for health care facilities," the authors write.
The authors include detailed algorithms for pre-exposure and post-exposure management of HCWs, as well as infection control management of varicella-zoster exposures.
They recommend that HCWs be screened for immunity at initial employment. Current employees could be screened when receiving their annual tuberculosis and immunization evaluation or through a special program. Employees with a history of VZV infection can be considered immune. Those without a definite history should undergo serologic testing; if negative, they should be immunized. The preferred test is latex agglutination, followed by an enzyme-linked immunosorbent assay or radioimmunoassay.
The following information should be recorded for each employee vaccinated: employee name, date, vaccine, manufacturer, lot number, site of immunization, and informed consent. Obtaining post-immunization serology is not recommended.
The employee health service should evaluate all employees potentially exposed to varicella or zoster as soon as possible. VZV infection in the source should be confirmed and the potential for VZV acquisition assessed. Employees with no history or an uncertain history of infection should be tested serologically for immunity. All susceptible employees should be considered for post-exposure prophylaxis with VZIG and removed from duty from days eight through 21 post- exposure. HCWs who develop varicella can return to work when clinically well and after all lesions are dried and crusted.
The EHS should evaluate all HCWs with VZV infection. Following confirmation of infection, exposed staff and patients should be managed appropriately. (A detailed table is provided.) All HCWs should be offered recommended therapy. (Another table specifies treatment.)
In conclusion, the authors call for more research in two areas: transmission risks of vaccine strain VZV to patients following employee immunization, and the correct post-exposure management of immunized HCWs exposed to VZV.
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