Pediatric Emergency Medicine

Pearls & Pitfalls - When Chicken Pox Doesn't Look Like Itself

Larry Mellick, MD, MS, FAAP, FACEP
Professor of Emergency Medicine
Medical College of Georgia

Davis L. Mellick, PA-S
Medical College of Georgia

Pearl: If a child who previously received the chicken pox vaccine presents with scattered papulovesicular lesions, consider breakthrough varicella in your differential.

Presentation: A 17-month-old African-American girl presented to the emergency department with oral lesions and pruritic blisters on her trunk that began the day before. She was also febrile at 38° C. The mother had given acetaminophen for fever control. A few papulovesicular lesions were evident on the front torso, and ulcerated vesicles were evident on the buttock and back. (See Figure 1and Figure 2.) There were also multiple lesions on the oral mucosa. The child lived at home with her mother and three other siblings and regularly attended a daycare facility. Her immunizations were current, and her varicella vaccination had been administered according to schedule.

Discussion: With the widespread use of the varicella vaccine since it was approved in 1995, the incidences of chickenpox have been reduced by as much as 90%.1,2 As a result, this once-common childhood illness may not be seen or recognized by new physicians. However, children still are at risk of breakthrough varicella despite more effective two-dose protocols. Breakthrough varicella is identified as wild-type chickenpox in children who have been immunized at least 42 days prior to the illness.3 While varicella-related hospitalizations have decreased by 75% and mortality rates have decreased by 82%, the potential for a lethal breakthrough still exists.3,4 A number of studies have suggested that children are more at risk of breakthrough if they have received the vaccine before 12 months, are in a mixed population of vaccinated and non-vaccinated, have a longer elapsed time since vaccination, and report a history of asthma or eczema.2,3,4,5 These risk factors still are debated and disputed by some.6 Identifying breakthrough varicella may be more difficult, as the lesions tend more toward papular or papulovesicular rather than vesicular, the number of lesions is small, and the lesions are distributed sporadically.7 The patient in the case presentation above had a mild infection with very few atypical appearing lesions and an unknown source of infection. With the growing rarity of the disease and the variation associated with breakthrough illness, this easily could be a missed diagnosis.


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  2. Vazquez M. Varicella infections and varicella vaccine in the 21 st century. Pediatric Infect Dis J 2004;23:9.
  3. Grose C. Varicella vaccination of children in the United States: Assessment after the first decade 1995-2005. J Clin Virology 2005;33:89-95.
  4. Creed R, Styaprakash A, Ravanfar P. Varicella zoster vaccines. Dermatologic Therapy 2009;22:143-149.
  5. Chaves SS, Gariullo P, Zhang JX, et al. Loss of vaccine-induced immunity to varicella over time. N Engl J Med 2007;356:1121-1129.
  6. Lee LE, Ho H, Lorber E, et al. Vaccine-era varicella epidemiology and vaccine effectiveness in a public elementary school population. Pediatrics 2008;121:e1548-e1554.
  7. Vasquez M, Shapiro ED. Varicella vaccine and infection with varicella-zoster virus. N Engl J Med 2005;325:439-440.


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