The kit is intended for professional use for the qualitative and semiquantitative detection of IgG antibodies to varicella zoster virus (VZV) in human serum or plasma and to determine the avidity of IgG antibodies. The test is also useful in the diagnosis of VZV-associated diseases, namely varicella and herpes zoster. The test can also be utilized for the differential diagnosis of neuroinfections (encephalitis, meningitis, cerebellitis, vasculitis, myelitis and inflammatory neuropathies), infections of the eye and of exanthematous diseases of the skin. The kit is intended for differentiation of primary and recurrent VZV infection. Primary infection induces mainly low avidity (bind with low affinity) IgG antibodies to viral antigens. Later, antibodies with high avidity prevail. The predominance of low avidity IgG antibodies indicates recent primary infection. In other words, individuals with predominance of high avidity antibodies underwent the primary infection in the past. If such individuals have the symptoms of active VZV infection, it usually means the reactivation of the infection.