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.

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.

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 patients 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.11,23,24

Active Immunization: Varicella Zoster Vaccines4,6,11

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

  1. physician-diagnosed varicella (chickenpox) or
  2. physician-diagnosed herpes zoster, or
  3. laboratory evidence of VZV immunity, or
  4. 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 varicella vaccine (Table 4) for the prevention of HZ in adults older than 60 years of age. It is derived from the same Oka strain of live attenuated VZV as Varivax.

Table 4. Varicella Zoster Vaccines.4,6
Vaccines Indications Schedules Adverse Effects
VarivaxPreexposure2 SC doses 4-8 weeks apartInjection site or generalized varicella-like rash (1-5%); fever (10%); anaphylaxis in persons with history of allergic reaction to neomycin or gelatin.
ZostavaxPrevention of HZ infection is susceptible patients ≥ 60 years old1 SC dose

Passive Immunization: Varicella Zoster Immune Globulin4,6

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™. It is available under an Investigational New Drug Application Expanded Access protocol from the FDA.