This patient should be given varicella-zoster immune globulin. Varicella-zoster is transmitted through infected respiratory secretions and, much less frequently, after direct contact with virus-containing cutaneous vesicular fluids. Persons with active varicella infection can shed virus beginning a few days before developing the typical rash. Susceptible household contacts are at greatest risk for contracting disease, which is estimated to occur at a rate of 90%. Historically, varicella is a childhood exanthem illness with limited morbidity and mortality providing life-long immunity thereafter, but infection in adults, pregnant women, and immunocompromised persons can result in more severe disease, at times resulting in death.
Following a known exposure to a person with varicella, the recommended postexposure prophylaxis to prevent varicella infection in nonimmune patients should be based on the type of exposure, susceptibility assessment, and risk factors for development of serious disease. When clinically warranted, postexposure preventive measures include active immunization or passive immunoprophylaxis. When administered within 3 to 5 days of exposure, the varicella vaccine has proved beneficial in preventing infection and diminishing disease severity in susceptible persons when infection occurs. However, this is a live-attenuated vaccine and is contraindicated in patients who are immunocompromised or taking immunosuppressive therapies, as well as in pregnant women. Under such circumstances, passive immunoprophylaxis using a purified human varicella-zoster immune globulin containing high levels of varicella-specific IgG antibodies is recommended and has been found to be most effective when administered within 4 days of exposure.
The efficacy of antiviral agents, such as acyclovir, to prevent postexposure development of varicella has not been proved and is not recommended.
Observation without providing postexposure prophylaxis may result in serious consequences in specific patient populations, including this patient, who is taking an immunosuppressive medication.