varicella-zoster%20virus%20infection%20(pediatric)
VARICELLA-ZOSTER VIRUS INFECTION (PEDIATRIC)
Varicella, also known as chickenpox, is a self-limited, benign disease caused by primary varicella-zoster virus (VZV) infection characterized by fever, malaise, and generalized pruritic vesicular rash.
The average incubation period is 14-16 days. It is transmitted via direct contact with vesicular fluid or inhalation of aerosolized respiratory secretions or via droplet route during face to face contact.
Hallmark sign is pruritic rash that begins in the scalp and face which eventually spreads to the trunks and extremities.

Monitoring

  • Further evaluation is needed especially in immunocompromised patients
  • Observe for the following in varicella zoster virus (VZV) infection:
    • Other bacterial, neurologic, respiratory, hepatic, hematologic complications
    • Appearance of rash in dermatomal distribution that is predictive of herpes zoster which usually follows latent period of many years
  • Observe for the following in herpes zoster:
    • Other bacterial, neurologic, ophthalmic, respiratory, hepatic, hematologic complications
    • Persistent pain after 1-3 months of rash resolution suggestive of postherpetic neuralgia

Prevention

  • Avoidance of varicella is the only guaranteed method of preventing complications
    • Patients infected with varicella zoster virus (VZV) are contagious for 24-48 hours prior to the emergence of clinical signs

Passive prophylaxis

Varicella Zoster Virus Immunoglobulin G (VZV IgG/ VZIG)

  • A high-titer preparation of VZV IgG antibodies
  • Recommended for susceptible high-risk individuals including:
    • Immunocompromised children without a history of VZV infection
    • Pregnant women without history of VZV & no Ab to VZV who have had a close exposure to an individual with varicella or herpes zoster
    • Newborn infants exposed to maternal varicella 5 days before to 2 days after birth
    • Premature infants ≥28 weeks age of gestation who were exposed to VZV during the neonatal period with mothers without immunity
    • Premature infants <28 weeks age of gestation or weighing ≤1000 g who were exposed to
    • VZV during the neonatal period regardless of mother’s immunity
    • <28 weeks AOG-born hospitalized premature infants regardless if the mother is with or without VZV infection
  • Not generally recommended in healthy susceptible adults since these patients can be given oral antivirals if varicella infection develops
  • Administer within 10 days post-exposure; ideally within 96 hours (4 days) post-exposure
  • Effects: Patients may still develop varicella despite VZIG but the risk of varicella pneumonia is significantly reduced if passive prophylaxis is used

Active prophylaxis

Varicella zoster virus, live attenuated (Varicella zoster virus vaccine)

  • Live attenuated vaccine of the Oka strain that provides long-lasting resistance against varicella
    • The vaccine strain causes subclinical VZV infection in vaccines & leads to immunity
    • As a live herpes virus, it may establish latency & reactivate later on
  • 1st dose may ideally be given to immunocompetent individuals 12-15 months of age who do not have a history of VZV infection
    • Contraindicated in immunocompromised patients 
  • 2nd dose should have been given in individuals 4-6 years
    • 2nd dose may be given before child reaches 4 years of age if ≥3 months has passed after 1st dose
  • Individuals ≥13 years of age, without previous VZV vaccination, should be given 2 doses 4-8 weeks apart; If 8 weeks elapsed, 2nd dose may be administered without restarting schedule
  • 2nd dose catch-up vaccine may be given 3 months after 1st dose in individuals ≤12 years of age & 4 weeks after 1st dose in individuals ≥13 years old
    • May also be given at longer interval

Combination measles, mumps, rubella & varicella, live attenuated (MMRV vaccine)

  • May be given to immunocompetent individuals >12 months to 12 years of age who do not have a history of VZV infection & requires simultaneous vaccine against measles, mumps & rubella
  • Not recommended in patients ≥13 years old

Post-exposure prophylaxis

Varicella zoster virus, live attenuated (Varicella zoster virus vaccine)

  • Varicella vaccine is recommended in susceptible individuals after exposure to varicella
  • Varicella vaccine is effective in preventing illness or modifying varicella severity if given within 3 days & potentially up to 5 days after exposure
  • If the exposure did result in infection it does not appear that administration of varicella vaccine during prodromal stage increases the risk for vaccine related adverse effects
  • Contraindicated in immunocompromised or pregnant patients
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