Varicella‑Zoster Serology: Evidence‑Based Recommendations for Immunity Assessment and Acute Diagnosis

Immunity Assessment

IgG serology is the preferred test to determine varicella immunity; IgM testing is not recommended for routine immunity screening. The CDC and the American Gastroenterological Association (AGA) advise using IgG alone because IgM provides no information on protective immunity. [1] [2]
Adults with uncertain or negative varicella history—especially those raised in tropical or subtropical regions—should have IgG testing to confirm immunity. (European Crohn’s and Colitis Organisation – ECCO) 3
Healthcare personnel lacking documented immunity require IgG testing to prevent nosocomial transmission. (CDC) 4
Pregnant women without documented immunity should undergo IgG testing because of fetal transmission risk and congenital varicella syndrome. (CDC) 4
Immunocompromised patients without documented immunity need IgG testing owing to their heightened risk for severe disease. (CDC) 4
Patients with inflammatory bowel disease or other immune‑mediated conditions who are candidates for immunosuppressive therapy should have IgG testing to decide whether pre‑treatment vaccination is required. (AGA) 2

A positive IgG result indicates immunity in both healthy and immunocompromised individuals, except bone‑marrow transplant recipients who should be considered non‑immune regardless of antibody status. (CDC) 1
A negative IgG result in a previously vaccinated person does not necessarily mean susceptibility, because commercial assays have suboptimal sensitivity for vaccine‑induced antibodies. (AGA; ECCO) [2] [3]
U.S. birth before 1980 is taken as evidence of immunity for most adults (excluding healthcare workers, pregnant women, and immunocompromised persons), since 96‑99 % of this cohort have serologic evidence of prior VZV infection. (CDC) 4

The CDC explicitly recommends against serologic testing (including IgM) before or after varicella vaccination due to low test sensitivity. (CDC) 2
IgM does not reflect immunity status; only IgG provides information about protective immunity. (CDC) [1] [4]

Clinical diagnosis based on the characteristic vesicular rash in a dermatomal distribution is the primary method for identifying varicella and herpes zoster. (ECCO) 3
When laboratory confirmation is needed (e.g., atypical presentation or immunocompromised host), PCR testing of vesicular fluid or lesion swabs is the gold standard, with sensitivity and specificity approaching 100 %. (ECCO) 3
Serology (IgG or IgM) is not useful for diagnosing acute chickenpox or shingles. (ECCO) 3

Do not use IgM to assess immunity; it provides no information on protective status. (CDC; AGA) [1] [2]
Do not rely on a negative IgG result in vaccinated individuals to infer susceptibility, because assays may miss vaccine‑induced antibodies. (AGA; ECCO) [2] [3]
Do not use serology to diagnose active varicella or herpes zoster; prefer clinical assessment or PCR. (ECCO) 3
Do not assume bone‑marrow transplant recipients are immune based on a positive IgG or prior history; they should be treated as non‑immune. (CDC) 1
Do not order post‑vaccination serologic testing to verify immune response, as available assays lack adequate sensitivity. (CDC) 4

Both healthy and immunocompromised individuals with verified positive varicella IgG may be considered immune (with the exception of bone marrow transplant recipients) 5, 6
Vaccination with the varicella vaccine serves as evidence of immunity 7

A positive varicella IgG test eliminates the need for varicella vaccination in most individuals 5, 6
Varicella-zoster immune globulin (VZIG) is not indicated for persons with documented immunity (positive varicella IgG) who are exposed to varicella 5, 7
Bone marrow transplant recipients should be considered non-immune regardless of previous history or positive antibody status 5, 6
Patients who received 2 doses of varicella vaccine before becoming immunocompromised are generally considered protected 5, 6

A negative antibody test in previously vaccinated individuals does not necessarily indicate susceptibility due to the low sensitivity of some tests to detect vaccine-induced antibodies 8
The CDC does not recommend serologic testing before or after immunization for varicella due to these limitations 8

Breakthrough varicella can occur in vaccinated individuals despite positive antibody status, though it is typically milder than disease in unvaccinated individuals 9