What are the criteria for evidence of immunity to varicella?

CDC considers evidence of immunity to varicella to be:

• Written documentation of 2 doses of varicella vaccine given no earlier than age 12 months with at least 4 weeks between doses.
• U.S.-born before 1980*
• A healthcare provider’s diagnosis of varicella or verification of history of varicella disease. When verifying a history of disease, a patient’s history should include an epidemiologic link to another typical varicella case or to a laboratory confirmed case, or evidence of laboratory confirmation, if testing was performed at the time of acute disease. In the absence of any of these criteria, the patient should not be considered to have evidence of immunity based upon a history of disease.
• History of herpes zoster, based on healthcare provider diagnosis or verification of disease history
• Laboratory evidence of immunity or laboratory confirmation of disease

*Note: Although there is only a very small chance of susceptibility, due to the potential for severe consequences from varicella infection, year of birth is not accepted as evidence of varicella immunity for healthcare personnel, immunosuppressed people, and pregnant people.