The Varicella Zoster Virus (VZV) Titer is a blood test that checks if you are immune to Varicella Zoster Virus, also known as Chickenpox and Shingles. It measures your antibody levels to get a sense for whether your immune system has the capability to respond to an infection with one of these diseases. Some people have had the chickenpox and developed immunity to varicella that way. Other people have developed immunity through receiving the Varicella vaccine series when they are young and/or receive vaccine boosters as adults.
As a consequence of either vaccination or prior exposure, people develop IgG antibodies to Varicella that provide immunity if they are exposed to the disease.