Chickenpox

Clinical features

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Subtypes and variants

Vaccine-associated chickenpox rash

• Etiology & Timing: Caused by live-attenuated Oka strain VZV vaccine; occurs 1–3 weeks post-vaccination in ~5% of patients.
• Clinical Features:
  • Sparse rash: Usually < 10 lesions (maculopapular or small vesicles on an erythematous base).
  • Distribution: Localized near injection site or mild generalized distribution.
  • Systemic symptoms: Minimal to absent (no or low-grade fever).
• Diagnosis:
  • Clinical: History of recent VZV vaccine (1–4 weeks) + mild, sparse vesicular rash.
  • Confirmatory: VZV PCR (distinguishes Oka vaccine strain from wild-type); indicated only if severe/immunocompromised.
• Key Differentials:
  • Wild-type Varicella: High fever, >200 lesions in various stages of development, exposure history.
  • Breakthrough Varicella: Wild-type infection occurring > 42 days post-vaccination.
• Management:
  • Immunocompetent: Supportive care only; cover lesions until fully crusted. No acyclovir needed.
  • Immunocompromised / Disseminated: Systemic Acyclovir (oral/IV).
  • Infection Control: Direct contact transmission possible; isolate from non-immune pregnant women, neonates, and immunocompromised individuals until crusted.

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Management

• Isolation & Infection Control:
  • Airborne + Contact precautions in hospital settings until all lesions are crusted.
• Supportive Care (Uncomplicated disease in healthy children <12 yo):
  • Symptomatic relief: Antihistamines for pruritus, acetaminophen for fever.
  • AVOID ASPIRIN due to severe risk of Reye syndrome.
• Antiviral Therapy (Oral Acyclovir or Valacyclovir):
  • Indications: Age ≥13 yo, chronic cutaneous/pulmonary disease, long-term salicylate/steroid use, complicated secondary cases.
  • Timing: Must initiate within 24 hours of rash onset to reduce severity/duration.
• IV Acyclovir:
  • Indications: Immunocompromised pts, severe/complicated disease (e.g., varicella pneumonia, encephalitis), or pregnant women w/ systemic complications.
• Post-Exposure Prophylaxis (PEP):
  • Immunocompetent & unvaccinated (≥1 yo): Varicella vaccine within 3–5 days of exposure. c
  • High-risk/Vaccine contraindicated (immunocompromised, pregnant, neonates w/ maternal infection 5 days before to 2 days after delivery): Varicella-Zoster Immune Globulin (VARIZIG) within 10 days (ideally ≤96 hr). If VARIZIG unavailable -> IVIG or oral acyclovir.