Immunization Status

Last Literature Review: February 2024 Last Update:

Medical Experts



Brian R. Jackson, MD, MS
Adjunct Professor of Pathology and Biomedical Informatics, University of Utah
Medical Director, Business Development, ARUP Laboratories


Patricia R. Slev, PhD, D(ABCC)
Professor of Pathology (Clinical), University of Utah
Section Chief, Immunology; Medical Director, Immunology Core Laboratory, ARUP Laboratories

Immunization status, or previous exposure to diseases, is often assessed using serology. This testing can evaluate protection from diseases such as pertussis, hepatitis A, hepatitis B, measles, mumps, rubella, chickenpox, shingles, and polio. Serologic investigation is especially useful for individuals with missing or incomplete vaccination records. Immunization status may be needed for various reasons, such as to inform decisions about vaccination, employment, school admission, or acceptance into an assisted living residence. Although laboratory test results can provide evidence of vaccination or exposure, there is no laboratory test available to definitively establish immunity.

Quick Answers for Clinicians

Where can I find information about immunization best practices?

The CDC provides up-to-date information for individuals  and healthcare providers.  This information is comprehensive and includes specific vaccination schedules for children 18 years or younger  and adults 19 years or older,  catch-up strategies for individuals who have missed vaccines,  vaccine administration guidelines,  safety information,  recommendations for the evaluation and vaccination of patients who have no (or questionable) vaccination records or who have been vaccinated outside of the United States,  and other educational materials.

What special testing considerations should be taken into account for pregnant individuals?

All pregnant patients should be evaluated for evidence of immunity to rubella and varicella-zoster viruses. Pregnant patients without evidence of immunity to these viruses should be vaccinated immediately after delivery. 

For all other diseases, the CDC recommendations for the use of serology testing for pregnant individuals with unknown vaccination status are the same as for all adults with unknown vaccination status. Serology testing can be used to determine immunization status, but revaccination is recommended. , 

How does laboratory testing provide evidence of immunization status?

Serology testing is used to detect antibodies that indicate previous vaccination or exposure to diseases. The results of these tests can be used to determine a medically appropriate vaccination schedule.

Where can I find more information about the diseases mentioned in this topic?

Refer to the following ARUP Consult topics for disease-specific information, such as detailed laboratory testing information and links to additional CDC resources: Bordetella pertussis - Whooping Cough, Viral HepatitisMeasles -Rubeola, Mumps VirusRubella - German Measles, and Varicella Zoster Virus - VZV.

Indications for Testing

Serology testing is a useful tool to determine immunization status or previous exposure to infectious agents, but testing should not be a barrier to the vaccination of individuals, especially those who are at high risk for exposure to vaccine-preventable diseases. Disease-specific serology testing recommendations can be found below.

Individuals who have complete medical records do not need serology testing to determine immunization status. However, these individuals should follow all CDC-recommended vaccination schedules for any missing vaccinations. , 

Hepatitis A Virus

Generally, if patients do not know whether they have been vaccinated against hepatitis A virus (HAV), the CDC recommends revaccination without serology testing.  However, serology testing can be performed to determine immunization status and whether or not vaccination is required. Prevaccination testing is most likely to be cost-effective for patients who were born or lived for an extended period in a geographic area with high or intermediate HAV prevalence.  Postvaccination serologic testing is not necessary after routine vaccination. However, testing for anti-HAV antibodies may be useful in some patients, including people with HIV infections and other immunocompromised individuals. 

Hepatitis B Virus

Generally, if patients do not know whether they have been vaccinated against HBV, the CDC recommends revaccination and serologic testing for hepatitis B surface antigen (HBsAg).  For healthcare providers (HCPs), serology testing to avoid unnecessary revaccination may be cost-effective.  Postvaccination serology testing is recommended for HCPs who are at high risk for occupational exposure to HBV and should be performed 1-2 months after vaccination. HCPs with a documented exposure to HBV should receive postexposure serology testing if they are unvaccinated or incompletely vaccinated or if they do not have documented proof of immunity. 

Measles, Mumps, and Rubella

Generally, if patients do not know whether they have been vaccinated against measles, mumps, and rubella, the CDC recommends revaccination without serology testing. Serology testing can be performed to determine immunization status and help determine whether vaccination is required.  Patients with well-documented, age-appropriate vaccination against measles, mumps, and rubella should not be revaccinated, even if serology test results show a negative or equivocal titer.  Prevaccination testing for HCPs without adequate presumptive evidence for immunity is generally not necessary. Serology testing is not recommended for HCPs with two documented doses of the measles, mumps, and rubella (MMR) vaccine.  Postvaccination and postexposure serology testing are not recommended for measles, mumps, and rubella.


If the pertussis vaccination status of a patient or HCP is unknown, age-appropriate vaccination (or revaccination) should be performed.  Serology testing is not an accurate measure of immunity because serologic correlates of protection have not been well established.  Prevaccination, postvaccination, and postexposure serology testing are not recommended. 


Generally, if patients do not know whether they have been vaccinated against varicella (chickenpox), the CDC recommends revaccination.  However, serology testing before vaccination is likely to be cost-effective in a healthcare setting.  If a person has received two documented doses of the varicella vaccine, serology testing is not recommended.  Postvaccination and postexposure serology testing are not recommended. 


Serologic testing to determine previous immunization to poliovirus is not recommended by the CDC. ,  If the vaccination status of a patient or HCP is unknown, age-appropriate vaccination should be performed without serology testing. 


Serology testing may be performed to monitor rabies immune status in individuals who have a high occupational risk of rabies exposure (eg, veterinarians) or after a confirmed occupational exposure. In some cases, serology testing may be useful to monitor the immune response in a person undergoing postexposure prophylaxis treatment. 

ARUP Laboratory Tests

NOTE: Laboratory tests cannot establish immunity to the diseases included in this topic; the laboratory tests discussed here can only provide evidence of vaccination or previous exposure.

Bordetella pertussis

(Refer to the ARUP Consult Bordetella pertussis - Whooping Cough topic for more information)

Hepatitis A

(Refer to the ARUP Consult Viral Hepatitis topic for more information)

Hepatitis B

(Refer to the ARUP Consult Viral Hepatitis topic for more information)


(Refer to the ARUP Consult Measles - Rubeola topic for more information)


(Refer to the ARUP Consult Mumps Virus topic for more information)


(Refer to the ARUP Consult Rubella - German Measles topic for more information)

Varicella-Zoster Virus

(Refer to the ARUP Consult Varicella-Zoster Virus - VZV topic for more information)