Acyclovir Post-exposure Prophylaxis for Varicella: Is it helpful?

Dose: 80 mg/kg/day in 4 divided doses for 7 days; maximum 800 mg 4 times a day

Time to start prophylaxis: 7-10 days after exposure (late incubation period)

Indication: People without evidence of immunity and with contraindications for varicella vaccination (VZIg) 1

acyclovir mechanism
CNX OpenStax [CC BY 4.0], via Wikimedia Commons

Results from some studies

Among 27 children in the treatment group, only 7.4% developed the disease while 77% of control subjects developed clinical varicella and seroconversion was observed in 63% of the patients. 2

Among 25 children in the treatment group, only 16% developed the disease while 100% of control subjects developed the disease. Seroconversion was observed in 85% of subjects. The incidence of fever and the severity of skin rashes were significantly lower in the treatment group. 3

Controversy

Some author mentions that additional data about acyclovir prophylaxis is needed because of the potential interference with the host response, which may predispose to early recurrent infection or incomplete protection from subsequent exposures, and enhanced selection of resistant VZV. He recommends, following the patient closely and giving the drug immediately after the onset of symptoms. 4

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