Immunization Status

Immunization status or previous exposure to diseases is often assessed using serology. This testing can evaluate protection from diseases such as Bordetella pertussis, hepatitis A virus (HAV), hepatitis B virus (HBV), measles, mumps, rubella, varicella zoster virus, and polio. Serologic investigation is especially useful for individuals with missing or incomplete vaccination records. Immunization status may be needed for various reasons, including 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 missing vaccines, vaccine administration guidelines, safety information, recommendations for the evaluation and vaccination of persons vaccinated outside of the United States, or those who have no (or questionable) vaccination records, and other educational material.

How does laboratory testing provide evidence of immunization status?

Serology testing is used to detect antibodies that are indicative of previous vaccination or exposure to diseases. The results of these tests can be used to inform the creation of a medically appropriate vaccination schedule.

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

Consult topics exist for Bordetella pertussis, hepatitis A virus (HAV), hepatitis B virus (HBV), measles, mumps, rubella, and varicella zoster virus. These topics include disease-specific information, including detailed laboratory testing information and links to additional CDC resources.

Indications for Testing

Serology 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 a high risk for exposure to vaccine-preventable disease. The CDC offers guidance for the use of serology to determine immunization status for individuals with complete medical records, those with missing or incomplete medical records, pregnant women, and healthcare workers (HCWs).

Those with Complete Medical Records

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

Those from Outside U.S. or with Incomplete Records

Individuals with incomplete, missing, or questionable medical records (eg, children adopted from outside the United States, recent immigrants) may require revaccination or serology testing. In general, vaccinations should be repeated in cases of uncertainty, but judicious use of serology can determine which vaccinations are needed for these individuals. 

Validation of vaccination status based on a person’s country of origin or vaccination records alone is often difficult. Individuals with written documentation that lists vaccination type, dates of administration, intervals between doses, and age at the time of vaccination that are generally consistent with the CDC recommendations   are more likely to be protected from exposure to vaccine-preventable diseases. However, because of variable vaccination standards and quality across countries, vaccination status is difficult to guarantee. The CDC provides vaccine-specific guidance in the Evaluation and vaccination of persons vaccinated outside of the U.S. who have no (or questionable) vaccination records. 

Pregnant Women

All pregnant women should be evaluated for evidence of immunity to rubella and varicella zoster virus during every pregnancy. Women without evidence of immunity to rubella and varicella should be vaccinated immediately after delivery. 

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

Healthcare Workers

Because HCWs are at risk for exposure to many serious diseases, the CDC provides specific vaccination requirements for these individuals. To comply with the CDC’s requirements, an HCW may provide medical documentation or up-to-date serology results that prove prior vaccination. Serology is not required, although in some situations it may be more cost-effective than revaccination of individuals with incomplete or missing records. If serology does not show evidence of prior immunization, or if the HCW has uncertain immunization status, revaccination according to established procedures is required.  After a vaccination series is completed, serology can be used to determine if a patient has responded to the vaccine.

Individuals with Needlestick Exposure

In some cases, serology can be used as an evaluation tool after a needlestick injury. If the vaccination status of an exposed individual is unknown, serology can aid in the determination of appropriate medical management. However, if postexposure prophylaxis is deemed necessary, it should begin without waiting for the test results. 

ARUP Lab 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 Bordetella pertussis topic for more information)

May be used as evidence of vaccination or past infection

Test does not determine immunity to B. pertussis

Hepatitis A

(Refer to the Hepatitis A Virus topic for more information)

May be used as evidence of vaccination or past infection

IgG does not appear until convalescent phase but remains detectable for life

Test does not determine immunity to HAV

Hepatitis B

(Refer to the Hepatitis B Virus topic for more information)

May be used as evidence of vaccination or past infection

Measles

(Refer to the Measles topic for more information)

May be used to detect evidence of vaccination or past infection

Test does not determine immunity to measles

Mumps

(Refer to the Mumps Virus topic for more information)

May be used to detect evidence of vaccination or past infection

Test does not determine immunity to mumps

Rubella

(Refer to the Rubella Virus topic for more information)

Determine immune status of females before pregnancy or for vaccination status

Test does not determine immunity to rubella

Varicella-Zoster Virus

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

Provide evidence of vaccination or past infection

Test does not determine immunity to varicella-zoster virus

Poliovirus

Detect neutralizing antibodies to poliovirus (types 1 and 3)

Medical Experts

Contributor

Jackson

Brian R. Jackson, MD, MS
Associate Professor of Clinical Pathology; Adjunct Associate Professor, Biomedical Informatics, University of Utah
Medical Director, Support Services, IT, and Business Development, ARUP Laboratories
Contributor

Slev

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

References

Additional Resources