A five-year-old girl, vaccinated against varicella-zoster virus (VZV) presented with clinical symptoms of herpes zoster in the 6th cervical dermatome. A VZV direct immune-fluorescence assay was negative three times but additional genotypical analysis showed a VZV strain genotype 2 (Oka vaccine strain). Therefore the diagnosis of a breakthrough varicella disease with the vaccine strain was established. An immunodeficiency was ruled out and the patient responded well to the initiated therapy. This case demonstrates that a negative VZV direct immunofluorescence assay does not exclude an infection with the vaccine strain.