Varicella and Herpes Zoster Infections

The varicella zoster virus (VZV) is transmitted from person-to-person by airborne droplets; contact with vesicular fluid, skin and mucous membranes; and freshly contaminated articles. The VZV is responsible for both chickenpox and herpes zoster (HZ) infections. Following initial exposure, after an incubation period of 14-16 days the patient develops a generalized papulovesicular rash. The period of communicability is 1 to 2 days before the onset of rash to 4-7 days after the appearance of the vesicles.²⁹

Primary infection usually occurs in childhood. Adults are at a much higher risk than children of developing serious complications, which include cerebellar ataxia, encephalitis and bacterial superinfections. Varicella in pregnant women is associated with a risk of intrauterine VZV infection, which might result in congenital varicella syndrome (highest risk during the 13-20 weeks of gestation), neonatal varicella, or herpes zoster during infancy and early childhood.²⁹

After primary infection, VZV remains dormant in sensory ganglia. When reactivated, the virus causes HZ, a painful vesicular rash typically appearing in a dermatomal distribution affecting one or two sensory nerve roots. The incidence and severity of HZ is age related, with over 50% of cases occurring in persons over 60 years of age. While patients with HZ may transmit the virus for one week after the lesions erupt, the risk for transmission is much lower than with chicken pox.³⁰

Active Immunization: Varicella Zoster Vaccines .^4,6

It is strongly recommended that all OHCP be immune to the VZV. OHCP are considered immune only if they have documentation of:

physician-diagnosed varicella (chickenpox) or
physician-diagnosed herpes zoster, or
laboratory evidence of VZV immunity, or
age-appropriate vaccination against the VZV.

There is one monovalent varicella vaccine (Varivax) licensed for use in adults (Table 4). It is derived from the Oka strain live attenuated VZV grown sequentially in cultures of human embryonic lung cells, embryonic guinea-pig cells, and human diploid cells. Zostavax is a high-potency formulation Varivax vaccine (Table 4) for the prevention of HZ in adults older than 60 years of age. A new adjuvanted recombinant subunit zoster vaccine (Shingrix) has superseded Zostavax as the vaccine of choice for HZ prevention and is recommended for immunocompetent adults ≥50 years age. Of note, individuals previously vaccinated with Zostavax are recommended to receive Shingrix vaccination.²⁰

Table 4. Varicella Zoster Vaccines.^4,6,20

Vaccines	Indications	Schedules	Adverse Effects
Varivax	Preexposure	2 SC doses 4-8 weeks apart	Injection site or generalized varicella-like rash (1-5%); fever (10%); anaphylaxis in persons with history of allergic reaction to neomycin or gelatin.
Zostavax	Prevention of HZ infection is susceptible patients ≥ 60 years old	1 SC dose
Shingrix	Prevention of HZ infection in susceptible patients ≥ 50 years old	2 IM doses at 0 and 2-6 months	Myalgia (45%), fatigue (45%), fever (21%), and injection-site pain (78%), redness (38%), and swelling (26%).

Passive Immunization: Varicella Zoster Immune Globulin ^4,6

ACIP recommends that varicella zoster immune globulin (VZIG) be administered within 96 hours of exposure for post-exposure prophylaxis in susceptible persons at high risk for varicella complications. This recommendation applies to women exposed to the VZV at any stage of pregnancy. The VZIG product currently used in the United States is VariZIG.

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