Varicella infection (chickenpox) – 8 Interesting Facts

What is Varicella infection (chickenpox)

Key Points

  1. Primary infection with varicella-zoster virus results in the rash of varicella (chickenpox); the virus establishes a latent infection in the nervous system and can reactivate later in life to cause herpes zoster (shingles)
  2. Rash evolves from macules to papules to vesicles, followed by pustules and then crusts; involvement begins on the head and trunk, spreading outwards, with new crops developing periodically over a few days, so that lesions of all stages may be seen at any site
  3. Oral acyclovir is recommended for treatment of persons at risk for severe infection, including adolescents, adults (including pregnant women), persons with chronic pulmonary or skin disease, and persons receiving salicylate therapy or short-term intermittent or aerosolized corticosteroids; it is most effective when begun within 24 hours of rash onset
  4. IV acyclovir is recommended for patients who are immunosuppressed or who have complications
  5. Most common complication in immunocompetent children is bacterial superinfection of skin lesions; other complications include cerebellar ataxia, encephalitis, viral pneumonitis, hepatitis, and thrombocytopenia
  6. Live attenuated varicella vaccine is recommended for all children aged 1 to 12 years and for persons aged 13 years and older without evidence of immunity to the virus
  7. Postexposure prophylaxis is recommended for susceptible persons who have been exposed, particularly if they are at risk for severe disease (eg, immunocompromised persons, pregnant women, neonates of mothers who developed chickenpox 5 days before to 2 days after delivery)
  8. For healthy immunocompetent persons, postexposure vaccine is recommended if given within 3 days of exposure. VariZIG (varicella-zoster immunoglobulin-human) is recommended within 10 days of exposure for persons at increased risk of severe disease if vaccine is contraindicated or more than 3 days have elapsed since exposure; a week of prophylactic acyclovir beginning 7 to 9 days after exposure is alternate option

Pitfalls

  • Varicella pneumonitis can escalate rapidly to respiratory failure; careful vigilance is required

Terminology

Clinical Clarification

  • Primary infection with varicella-zoster virus results in the highly contagious febrile exanthematous illness varicella, commonly called chickenpox
    • A second episode of chickenpox is rare in immunocompetent persons; however, the varicella-zoster virus establishes a latent infection in the nervous system and can reactivate later in life to cause herpes zoster (shingles)

Classification

  • Varicella-zoster virus is a double-stranded DNA virus belonging to the herpesvirus family 1

Diagnosis

Clinical Presentation

  • From Paller AS et al: Exanthematous diseases of childhood. In: Paller AS et al, eds: Hurwitz Clinical Pediatric Dermatology. 5th ed. Philadelphia, PA: Elsevier; 2016:382-401, Figure 16-1.Varicella. – Note the early lesions consisting of erythematous macules and papules and the well-developed vesicular lesion.
  • From Warris A et al: Viral exanthems. In: Cohen J et al, eds: Infectious Diseases. 3rd ed. London, England: Mosby; 2010:99-108, Figure 8.1a.The lesions of varicella (chickenpox). – At the same time papules, vesicles and pustules, some of which are beginning to crust from the center, are seen.
  • From Warris A et al: Viral exanthems. In: Cohen J et al, eds: Infectious Diseases. 3rd ed. London, England: Mosby; 2010:99-108, Figure 8.1b.The lesions of varicella (chickenpox). – At the same time papules, vesicles and pustules, some of which are beginning to crust from the center, are seen.

History

  • Onset of illness is 7 to 21 days after exposure to source 1
  • Illness begins with fever, headache, and malaise, followed within 1 to 2 days by appearance of a rash, which is often intensely pruritic 2
  • Fever and other constitutional symptoms usually resolve within 2 to 4 days after appearance of rash 3
  • Eruption appears first on the scalp and face, then spreads to the trunk and, later, to the extremities
  • In typical cases, new lesions continue to appear in crops over 1 to 6 days, 1 generally peaking at about 48 hours; 4 duration may be prolonged in immunocompromised persons
  • Symptoms associated with severe disease include dyspnea, cough, bleeding, and persistent fever with development of new lesions beyond 6 days 4
  • In immunosuppressed patients, abdominal pain may indicate visceral involvement; patient who have undergone bone marrow transplant may experience right upper quadrant pain caused by severe liver involvement 4

Physical examination

  • Children with varicella may show some lassitude and discomfort, but generally do not appear severely ill
  • Adolescents and adults may appear systemically ill
  • Fever usually peaks around 38.9°C, but may be as high as 41.1°C in children 3
  • Lesions evolve from macules to papules to thin-walled vesicles, which become cloudy or pustular in appearance and may umbilicate before crusting
  • Presence of lesions in various stages of healing is characteristic 3
  • Typically 200 to 500 lesions are scattered over the body; more densely concentrated in central areas 2
  • Mucosa (ie, conjunctival, nasal, oral, vaginal) can also be involved
  • Crusted lesions slough after 1 to 2 weeks 5
  • Pigmentation changes (eg, hyper- or hypopigmentation) at the lesion site may persist in some patients for weeks; scarring is unusual in the absence of local secondary infection 3
  • In immunocompromised persons, skin lesions may be hemorrhagic or verrucous
  • Patients with varicella pneumonia may be tachypneic and crackles may be evident, but clinical signs often are absent 4
  • Children with cerebellar ataxia (which may present concurrently or after the acute illness) may exhibit nystagmus and/or tremor of head or extremities with movement, in addition to ataxic gait 6
  • Physical examination indicators of severe disease include pulmonary findings, dense crops of vesicles, hemorrhagic rash or bleeding from any other location (eg, gums, gastrointestinal tract), and neurologic changes 4
  • Patients with breakthrough varicella (defined as occurring despite having received vaccine more than 42 days prior) may have very few lesions 7
  • Occasionally, varicella occurs as a subclinical illness, without a recognized eruption

Causes and Risk Factors

Causes

  • Primary varicella infection can occur after exposure to either chickenpox or shingles
    • 60% to 90% of susceptible contacts with household exposure to varicella develop infection; 20% to 30% of susceptible persons exposed to herpes zoster become infected 2
  • Virus is spread by respiratory droplets, by aerosolization of infectious material in lesions or on fomites (eg, bedding), or by direct contact with cutaneous lesions 1 8
  • May be spread transplacentally to the fetus of a pregnant woman who acquires chickenpox

Risk factors and/or associations

Age
  • Occurs most commonly during childhood in temperate climates
    • Before the advent of an effective vaccine, more than 95% of children in temperate climates were infected with varicella-zoster virus, usually before age 5 years 2
  • Infection is usually delayed until adolescence or adulthood in tropical climates
Other risk factors/associations
  • Occurs most often in winter and spring in temperate climates, or during the cooler, drier seasons in tropical climates
  • Risk factors for severity include age (adolescence or adulthood), pregnancy, impaired cellular immunity (including AIDS), and perinatal acquisition (infants whose mothers have varicella 5 days before to 2 days after delivery) 1 2 8
    • Risk of severe disease is 15 9 to 25 10 times greater for adults than for children
  • Preexisting lung disease and smoking are risk factors for development of varicella pneumonia 4

Diagnostic Procedures

  • From Chen F-L et al: Fatal vericella infections in a young patient with systemic lupus erythematosus. J Exp Clin Med. 6(5):168-9, 2014, Figure 1.Chest radiograph reveals interstitial infiltration of the bilateral lower lobe of the lungs.
  • From Das D et al: Chest x-ray manifestations of pneumonia. Surgery. 27(10):453-5, 2009, Figure 2.Nodular consolidation in a patient with chickenpox; multiple rounded opacities can be seen throughout both lungs.
  • From Hansell DM et al: The immunocompromised patient. In: Hansell DM et al, eds: Imaging of Diseases of the Chest. 5th ed. London, England: Mosby; 2010:295-384, Figure 6.68.Varicella pneumonia in a man with acute myelocytic leukemia. – Frontal chest radiograph shows bilateral coarse nodular opacities that are confluent in the perihilar regions.

Primary diagnostic tools

  • Diagnosis is established by clinical presentation alone in most cases 2
    • A disseminated vesicular rash with characteristic lesions in various stages of evolution is usually sufficient for a diagnosis of varicella 2
  • Laboratory testing for confirmation may be appropriate in the following circumstances: 10
    • Unusual presentation, diagnostic uncertainty
    • Suspected breakthrough infection in vaccinated person
    • Immunocompromised persons
    • Infection control concerns, need for postexposure prophylaxis
  • Options for laboratory confirmation, when indicated, include:
    • Polymerase chain reaction for varicella-zoster virus 10
      • Test of choice
    • Direct fluorescent antibody or special stains (Tzanck smear) 2
    • Culture 10
    • Acute and convalescent serologic testing for varicella-zoster virus 10
      • May be useful to establish the diagnosis retrospectively
      • Sometimes useful to determine immune status in those who have been exposed and who may benefit from postexposure prophylaxis, though false-negative and false-positive results occur 7
  • Other laboratory testing (eg, CBC, chemistry) is usually not necessary for the diagnosis, but may be done if complications are suspected or if alternate diagnoses are considered
  • Obtain chest radiograph and pulse oximetry in any patient at risk of varicella pneumonia and in any patient with symptoms or signs suggesting pulmonary involvement 4

Laboratory

Imaging

Other diagnostic tools

Differential Diagnosis

Most common

  • Impetigo
    • Bacterial skin infection common in young children
    • Like varicella, presents with vesicular lesions that progress to crusts, often on the face and/or extremities
    • Unlike varicella, fever is uncommon, and lesions are usually confined to a relatively small area, not generalized
    • Distinction is usually made clinically; while diagnosis of impetigo is supported by demonstration of gram-positive cocci on Gram stain and culture of Staphylococcus aureus or Streptococcus pyogenes, these organisms can secondarily infect varicella lesions
  • Enterovirus infection
    • Infection caused by a variety of enteroviruses and related species, commonly affecting young children
    • Similar to varicella, causes mild febrile illness that may be accompanied by a rash; vesicular rash is associated with certain serotypes of Enterovirus and Coxsackie species
    • Unlike varicella, these vesicular rashes tend to be densest at the periphery (eg, hands, feet); involvement of oral mucosa is more common and more pronounced
    • Distinction is usually made on clinical grounds; if laboratory documentation is necessary, vesicular fluid may be tested by nucleic acid amplification techniques
  • Herpes simplex infection
    • Primary or reactivation infection caused by human herpesvirus 1 or human herpesvirus 2
    • Like varicella, primary infection may be associated with fever and vesicular rash
    • Unlike varicella, eruption is usually perioral; primary infection also may be associated with extensive painful vesicular lesions of the oropharyngeal mucosa
    • Distinction is usually clinical, but polymerase chain reaction can be used to make a definitive diagnosis
  • Stevens-Johnson syndrome
    • Potentially severe blistering skin condition that may result in extensive skin loss and multiorgan failure
    • May begin in a manner similar to varicella, with macular lesions that become vesicular
    • Unlike varicella in immunocompetent persons, lesions of Stevens-Johnson syndrome enlarge, coalesce, and slough, leaving large areas of denuded skin; often associated with mucosal involvement and significant systemic illness
    • Diagnosis is confirmed by biopsy
  • Guttate psoriasis
    • Inflammatory skin condition of unknown cause, but commonly preceded by streptococcal pharyngitis
    • Characterized by abrupt onset of multiple, scattered papules
    • Unlike varicella, these lesions evolve as plaques and persist for weeks or longer
    • Diagnosis is clinical; may be confirmed by biopsy if necessary
  • Pityriasis rosea
    • Skin condition of uncertain cause, commonly affecting children
    • May begin with mild systemic symptoms, followed by gradual appearance of a rash
    • Unlike varicella, rash is usually not vesicular, and scalp and face are relatively spared; progression continues over weeks to a few months
    • Distinction is made clinically
  • Smallpox
    • Severe and highly contagious illness caused by variola virus, which is no longer naturally occurring, but is a potential bioterror weapon
    • Like chickenpox, characterized by fever and vesicular skin eruption
    • Patients with smallpox tend to be more profoundly ill, with higher fever, prostration, and severe back or abdominal pain; lesions are numerous, thick-walled, and tense, beginning in the mouth and distal extremities (eg, palms, soles) before spreading centrally, all in the same stage of development at any particular body site
    • Diagnostic testing by polymerase chain reaction and/or culture can be arranged through public health authorities

Treatment

Goals

  • Hasten recovery
  • Prevent complications
  • Reduce transmission

Disposition

Admission criteria

Immunocompromised persons and patients with severe disease (including complications) should be admitted for IV antiviral therapy

Criteria for ICU admission
  • Patients with severe pulmonary, central nervous system, or infectious complications may require intensive care

Recommendations for specialist referral

  • Infectious disease consultation may be required if there is doubt about the diagnosis, or if the patient has complications caused by virus itself or by bacterial superinfection
  • Consult dermatologist for diagnostic uncertainty
  • Consult pulmonologist for patients with varicella pneumonia
  • Consult neurologist to evaluate and manage neurologic complications (eg, ataxia, meningitis, encephalitis)

Treatment Options

Most healthy children require only symptomatic care to relieve pruritus and fever; acetaminophen is recommended over aspirin (which is associated with Reye syndrome) or ibuprofen (which may be associated with an increased risk of complications caused by group A streptococcus) 8

  • Antiviral treatment is not recommended for otherwise healthy children because it only modestly decreases symptoms by about 1 day 2
  • Administer antiviral therapy to otherwise healthy children who have a nonimmune sibling or other household member with a medical condition that increases the risk of severe disease 4

Oral acyclovir is recommended for persons at risk for severe disease or complications: 12

  • Adolescents and adults
  • Persons with chronic cutaneous or pulmonary conditions
  • Persons receiving long-term salicylate therapy
  • Persons receiving short-course, intermittent, or aerosolized corticosteroids

Oral valacyclovir or famciclovir have a more convenient dosing schedule and result in higher antiviral drug levels than does oral acyclovir, so these are favored by some experts over acyclovir 8

  • Both can be used in adults; oral valacyclovir is also approved for treatment of children aged 2 years to 18 years with varicella 2

Although acyclovir is an FDA category B drug, most experts recommend treatment of pregnant women with varicella because of the high risk of severe complications, including death 13 14

  • The Acyclovir Pregnancy Registry collected data from 1984 through 1997 on 1127 women who received acyclovir during pregnancy (including 712 with first trimester exposure); there was no difference in the incidence of birth defects between this group and the general population 15
  • Less published experience is available about valacyclovir, but the risk is considered low 16

IV acyclovir is recommended in the following circumstances: 12

  • Severe disease or complications (eg, varicella pneumonia, encephalitis, thrombocytopenia, hepatitis)
  • Immunocompromised patients, including those receiving high-dose corticosteroids (eg, equivalent of prednisone 2 mg/kg/day 7 or higher) for more than 14 days
    • Acyclovir reduces visceral dissemination in immunocompromised persons, in whom IV acyclovir is recommended for 7 to 10 days or until all lesions have crusted 2
  • Perinatal chickenpox (first 2 weeks of life) 4 17

Antiviral therapy is most effective when started within 24 hours of first skin lesions

Drug therapy

  • Acyclovir
    • For immunocompetent patients:
      • Acyclovir Oral suspension; Children >= 2 years and Adolescents: 20 mg/kg/dose PO 4 times per day (Max: 800 mg/dose) for 5 days. Initiate at first sign of symptoms (i.e., within 24 hours).
      • Acyclovir Oral tablet; Adults: 800 mg PO 4 times per day for 5 days. Initiate therapy at the first sign of symptoms (i.e., within 24 hours).
    • For immunocompromised patients and/or patients with severe infection:
      • Acyclovir Sodium Solution for injection; Neonates: 10 to 20 mg/kg/dose IV every 8 hours.
      • Acyclovir Sodium Solution for injection; Infants: 10 mg/kg/dose or 500 mg/m2/dose IV every 8 hours for 7 to 10 days or until no new lesions for 48 hours.
      • Acyclovir Sodium Solution for injection; Children: 10 mg/kg/dose or 500 mg/m2/dose IV every 8 hours for 7 to 10 days or until no new lesions for 48 hours.
      • Acyclovir Sodium Solution for injection; Adults and Adolescents: 10 to 15 mg/kg/dose IV every 8 hours for 7 to 10 days for HIV-infected patients with severe or complicated disease; switch to oral therapy after defervescence if there is no evidence of visceral involvement. Use ideal body weight for obese patients.
  • Valacyclovir
    • Valacyclovir Hydrochloride Oral tablet; Children >= 2 years: 20 mg/kg/dose PO three times daily for 5 days in immunocompetent patients (Max: 3 g/day). Start treatment at the first sign or symptom, preferably within 24 hours of rash onset.
    • Valacyclovir Hydrochloride Oral tablet; Adolescents: 20 mg/kg/dose PO 3 times daily for 5 days in immunocompetent patients (Max: 3 g/day). Start treatment at the first sign or symptom, preferably within 24 hours of rash onset. HIV guidelines recommend 1 g PO three times daily for 5 to 7 days for uncomplicated infections; 1 g PO three times daily as stepdown therapy from IV acyclovir for complicated infections, for a total treatment course of 7 to 10 days.
    • Valacyclovir Hydrochloride Oral tablet; Adults†: HIV guidelines recommend 1 g PO three times daily for 5 to 7 days for uncomplicated infections; 1 g PO three times daily as stepdown therapy from IV acyclovir for complicated infections, for a total treatment course of 7 to 10 days.
  • Famciclovir
    • Famciclovir Oral tablet; Adults: 500 mg PO 3 times daily for 5—7 days is recommended by the HIV guidelines for uncomplicated infections or as stepdown treatment from IV acyclovir for a total treatment course of 7—10 days in patients with complicated infections.

Nondrug and supportive care

  • OTC antipruritic medication, mouthwashes, and topical anesthetic may provide some relief 4
  • Trim children’s nails to prevent excoriation from scratching, which may promote bacterial superinfection

Comorbidities

  • Immunocompromised persons (especially those with defects in cell-mediated immunity, which may result from high-dose corticosteroids) are at increased risk for severe disease and complications; these patients require IV acyclovir to be initiated as soon as possible once the diagnosis is suspected 12
  • Treatment is also recommended in patients of all ages with the following conditions: 12
    • Chronic cutaneous or pulmonary conditions
    • Receiving long-term salicylate therapy
    • Receiving short-course, intermittent, or aerosolized corticosteroids

Special populations

  • Healthy persons at high risk for severe disease likely to benefit from antiviral therapy include:
    • Adolescents and adults, including pregnant women 12
    • Neonates who develop varicella within the first 2 weeks of life 17
  • Patients with renal insufficiency require adjustment of antiviral drug doses

Monitoring

  • Monitor renal function in patients receiving IV acyclovir
  • Monitor oxygen saturation in patients with pulmonary symptoms or documented pneumonitis

Complications and Prognosis

Complications

  • From Ozaki T et al: Development of varicella vaccine in Japan and future prospects. Vaccine. 34(29):3427-33, 2016, Figure 1.Impetigo caused by Staphylococcus aureus superimposed on vesicles (1-year-old boy).
  • Most common complication of varicella is bacterial superinfection of skin lesions
    • Group A streptococcus or Staphylococcus aureus infections can cause cellulitis and, occasionally, life-threatening necrotizing fasciitis
    • A significant increase in temperature several days into the illness should prompt evaluation for bacterial complications
  • Complications involving the lungs and liver may occur during the acute course, and they are more common in children with impaired cellular immunity (including those receiving systemic steroids), children with chronic pulmonary or skin disease, adults, and pregnant women during the third trimester
    • Pulmonary involvement occurs in 5% to 14% of adults with chickenpox 4
    • Varicella pneumonia can evolve quickly to severe respiratory compromise requiring mechanical ventilation and may be fatal, especially in pregnant women
  • Cerebellar ataxia is a relatively common complication that occurs during the acute illness or in the immediate aftermath (1-3 weeks after rash onset) and generally resolves within 2 to 4 weeks 9
  • Less frequent neurologic complications include viral meningitis, encephalitis, and vasculopathy (which presents as a stroke); the latter may present up to a year after the acute illness 18
  • Thrombocytopenia may occur in the immediate postinfection period and may be profound
  • Purpura fulminans (arterial thrombosis) is a rare but very severe complication and may be fatal
  • Reye syndrome, characterized by liver dysfunction and encephalopathy, is precipitated by the use of salicylates in viral illness. Frequency has declined significantly with the recognition that it can be prevented by avoiding salicylate use in children; it remains a risk in children who require chronic aspirin therapy
  • Congenital varicella syndrome occurs in the infants of 1% to 2% 1 of women who develop varicella infection, primarily in the first 20 weeks of pregnancy; affected infants are small for gestational age, commonly demonstrate a dermatomal rash similar to shingles, and may have a variety of neurologic, ocular, and musculoskeletal anomalies 14
    • Risk is highest between 13 and 20 weeks of gestation 4
    • Offer fetal ultrasonography to women who develop chickenpox during pregnancy (especially between 13 and 20 weeks of gestation) to evaluate morphologic changes suggesting congenital varicella syndrome 16 19
      • The value of amniocentesis in this setting is unclear; a negative polymerase chain reaction result correlates well with absence of fetal infection, but a positive result does not necessarily confirm infection of the fetus 16
    • Spontaneous abortion, fetal demise, and premature labor are occasional complications of varicella infection during pregnancy 16
  • Patients with AIDS and moderately reduced CD4 cell counts may develop recurrent varicella lesions in the absence of new exposures, and patients with CD4 cell counts below 200/µL may develop progressive varicella with new lesions occurring for at least 1 month or chronic verrucous lesions 2
  • Varicella-zoster virus establishes a latent infection in the nervous system and can reactivate later in life to cause herpes zoster (shingles)

Prognosis

  • In immunocompetent children, disease is self-limited, prognosis is excellent, and lifelong immunity results; mortality rate is less than 2 per 100,000 cases 9
  • Prognosis is less favorable in adults, whose mortality rate is about 25 times that of children 20
  • Pregnant women have 5 times the mortality of nonpregnant adults; risk is highest after 20 weeks of gestation 4
  • Neonates born to women who develop chickenpox 5 days before to 2 days after delivery are at high risk for severe infection with a mortality rate of 30% without treatment 4

Screening and Prevention

Screening

At-risk populations

  • Consider screening for all adolescents and adults, particularly women of child-bearing age 7 17
  • Screen all pregnant women for evidence of immunity 7 13 17 19
  • Screening for immunity may be indicated in other circumstances in which exposure has occurred or as a public health measure (eg, health care employment, school enrollment) 7

Screening tests

  • Evidence of immunity may be based on laboratory, clinical, or epidemiologic criteria, including any of the following: 7
    • Written documentation of age-appropriate vaccination
    • Laboratory evidence of immunity or laboratory confirmation of disease
    • Health care provider diagnosis or verification of disease
    • History of health care provider–diagnosed herpes zoster
    • For persons other than pregnant women and health care providers, history of birth in the United States before 1980 is also considered evidence of immunity because of the high rate of endemicity in the prevaccine era

Prevention

  • Varicella vaccine
    • Live attenuated varicella vaccine is recommended for children aged 1 to 12 years and for those aged 13 years and older without immunity to the virus 21
    • 2 doses of vaccine are given subcutaneously 21
      • For children:
        • First dose age: 12 to 15 months
        • Second dose age: 4 to 6 years
        • If catch-up dose(s) are needed for children younger than 13 years old, administer 3 or more months apart
      • For adolescents and adults:
        • Give 2 doses 4 to 8 weeks apart (first dose need not be repeated if more than 8 weeks have elapsed)
        • Postpartum women who do not have evidence of immunity should receive the first dose of vaccine after delivery and before hospital discharge, followed by a second dose in 4 to 8 weeks; breastfeeding is not a contraindication
    • The varicella vaccine may also be given as part of a combined measles, mumps, and rubella (MMR) vaccine for children aged1 to 12 years in the United States 7
    • Vaccine is 75% to 90% effective in protecting against symptomatic varicella and more than 95% effective in protecting against severe disease 2
    • Most common complications of varicella vaccination are pain at the injection site, fever, and a mild rash (incidence about 5%) within 2 weeks after vaccination 10
      • Rash is usually localized to area of vaccination and is often papular; in some healthy persons, rash can be disseminated, although there are fewer lesions and symptoms are much less severe than with wild-type virus 2
      • In persons with severely impaired cellular immunity, rash is more common, can be extensive, and may be accompanied by organ dysfunction 2
    • Vaccine strain of varicella has very rarely been transmitted to other people, but only by vaccinees who developed a rash 21
    • Varicella vaccine establishes latency and can cause shingles, although this complication occurs less commonly with vaccine virus than with wild-type virus 2
    • Varicella vaccine is contraindicated in the following cases: 21
      • Women who are (or may be) pregnant
        • A review of 629 pregnancies during which vaccine was inadvertently administered did not reveal any cases of congenital varicella syndrome or association with any other birth defect 22
      • Persons receiving high-dose immunosuppressive therapy (eg, 2 mg/kg or more of prednisone daily)
      • Persons with hematologic malignant neoplasms
      • Family history of congenital hereditary immunodeficiency (unless known to be immunocompetent)
      • Recent (up to 11 months) receipt of blood products
    • Consider vaccination HIV-infected children with age-specific CD4 T cells of 15% or more and adolescents and adults with CD4 T cell counts of 200 cells/µL or higher 21
  • Postexposure prophylaxis
    • Indicated for susceptible persons at high risk for severe infection or complications, after exposure to chickenpox or disseminated herpes zoster; risk is less (but not nonexistent) for localized shingles 20
      • Significant exposures include the following:
        • Household contact
        • Face-to-face contact (duration not clearly defined, but some experts consider 5 minutes sufficient)
        • Hospital roommate
    • For healthy immunocompetent persons, varicella vaccine is preferred; administer as soon as possible after exposure, preferably within 72 hours 7
      • Found to be 70% to 90% effective in healthy persons in preventing illness if given within 5 and 3 days of exposure, respectively 20
    • VariZIG (varicella-zoster immunoglobulin-human) is indicated for susceptible exposed persons at risk for severe varicella when vaccine cannot be given or when time frame for vaccine has passed
      • Recommended for the following groups: 7
        • Immunocompromised patients
        • Neonates born to mothers who develop varicella between 5 days before and 2 days after delivery
        • Preterm infants born at 28 weeks of gestation or later who are exposed during the neonatal period and whose mothers do not have evidence of immunity
        • Preterm infants born at less than 28 weeks of gestation or who weigh 1000 g or less at birth and are exposed during the neonatal period, regardless of the mother’s immune status
        • Pregnant women who have no evidence of immunity
      • Recommended dosages:
        • 2 kg or less: 62.5 international units/dose (one-half vial) intramuscular
        • 2.1 to 10 kg: 125 international units/dose (1 vial) intramuscular
        • 10.1 to 20 kg: 250 international units/dose (2 vials) intramuscular
        • 20.1 to 30 kg: 375 international units/dose (3 vials) intramuscular
        • 30.1 to 40 kg: 500 international units/dose (4 vials) intramuscular
        • 40.1 kg or more: 625 international units/dose (5 vials) intramuscular
      • Approved for use up to 10 days after exposure, but should be given as soon as possible 23
      • Prevents or attenuates varicella in 90% of susceptible persons if given within 4 days of exposure 2
      • IV immunoglobulin 400 mg/kg may be administered if VariZIG is not available 24
    • As a third alternative when neither active nor passive immunization is feasible, oral acyclovir may be administered for a week beginning 7 to 9 days after exposure 2
      • Recommended dosage is 20 mg/kg/dose (Max: 800 mg/dose) 4 times daily for children and 800 mg 5 times daily for adults
      • Estimated to be 80% to 85% effective as postexposure prophylaxis
  • Infection control in the hospital
    • Patients require placement in a negative pressure room; airborne and contact precautions are recommended
    • Contact precautions are necessary for immunocompetent persons with localized herpes zoster

Sources

  1. Alter SJ et al: Common childhood viral infections. Curr Probl Pediatr Adolesc Health Care. 45(2):21-53, 2015 Reference