A boy aged 19 months presented with pruritic vesicular lesions associated with an erythematous rash over the left leg (Figs. 1 and 2) with onset two days prior. He did not have fever or general malaise. His vaccines were up to date. He had no lesions elsewhere in the body nor household contacts with the same symptoms. The PCR test of a skin swab sample was positive for varicella-zoster virus (VZV), prompting initiation of treatment with acyclovir at a dose of 200mg every six hours. At seven days of treatment, the patient only had residual lesions and had not developed complications.

Figure 1.

Fluid-filled blisters associated with a red rash on the medial and outer aspects of the left leg.

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Figure 2.

Herpes-zoster lesions on the inner aspect of the left leg.

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The patient had received the first dose of varicella vaccine at age 15 months in the left thigh, even though the preferred injection site from age 1year is the deltoid region.

The varicella vaccine contains live, attenuated VZV derived from the Oka strain.1 While the incidence of VZV reactivation is lower with the vaccine strain compared to the wild-type strain,2 the potential for reactivation of the vaccine strain demands that clinicians ask about the site of injection regardless of age. Cases of vaccine strain reactivation seem to be milder compared to reactivation after primary infection.3