How to Prove Immunity When Your Vaccine Records Are Lost

What is a titer test and how does it work?

A titer (pronounced TY-ter) is a blood test that measures the concentration of antibodies to a specific pathogen. Antibodies are proteins your immune system produces — whether from vaccination or past infection — to recognize and fight that pathogen in the future.

A lab reports the result as a number. Above a defined threshold it is read as 'immune' or 'reactive,' meaning you likely have protective immunity. Below that threshold it is 'non-immune' or 'non-reactive,' suggesting you may need a vaccine dose.

The Advisory Committee on Immunization Practices (ACIP) recognizes serologic evidence of immunity as an acceptable alternative to documented vaccination for certain vaccines 1Ref 1Wodi AP, Issa AN, Moser CA, Cineas S (2025).Advisory Committee on Immunization Practices Recommended Immunization Schedule for Adults Aged 19 Years or Older — United States, 2025.Serologic evidence of immunity as acceptable alternative to documented vaccination; guidance on pre-1957 birth-year presumptive immunity; re-vaccination safety; ACIP recognition of titers for MMR, varicella, hepatitis B..

Which diseases can be tested with titers?

Titer tests exist for most routinely vaccinated diseases. Common ones include:

• MMR (measles, mumps, rubella IgG antibodies) — frequently required by colleges, healthcare employers, and graduate programs
• Varicella (chickenpox) IgG — high rates of natural immunity exist in adults who grew up before the vaccine era; a titer can confirm this without re-vaccination
• Hepatitis B surface antibody (anti-HBs) — required for healthcare workers and many laboratory settings 2Ref 2Centers for Disease Control and Prevention (2024).Hepatitis B Vaccine Administration.Anti-HBs ≥10 mIU/mL after completing hepatitis B series as the correlate of protection; titer testing used for healthcare workers and others needing documented proof of immunity.
• Hepatitis A IgG — occasionally requested for international travel or certain occupational settings

A clinician will choose which titers make sense based on your age, history, and what institution needs the documentation.

When is re-vaccination the better choice?

Titer testing adds a lab cost and a waiting period. For some vaccines — particularly MMR, varicella, and the hepatitis B series — receiving the doses again is considered safe even if you were previously vaccinated. Getting an extra dose does not cause harm; your immune system mounts a booster-like response.

If cost or turnaround time is a barrier, your clinician may recommend re-vaccination instead of titers. This is a reasonable and common approach that the ACIP schedule explicitly supports 1Ref 1Wodi AP, Issa AN, Moser CA, Cineas S (2025).Advisory Committee on Immunization Practices Recommended Immunization Schedule for Adults Aged 19 Years or Older — United States, 2025.Serologic evidence of immunity as acceptable alternative to documented vaccination; guidance on pre-1957 birth-year presumptive immunity; re-vaccination safety; ACIP recognition of titers for MMR, varicella, hepatitis B..

What to do before ordering titers

Before paying for a blood test, search for your records first:

1. Contact your childhood pediatrician's office (or the practice that absorbed their records). 2. Check your state's immunization information system (IIS) — most states maintain digital registries accessible through the CDC's IIS contacts page 3Ref 3Centers for Disease Control and Prevention (2024).Contacts for IIS Immunization Records.State-by-state directory of immunization registry contacts for patients recovering lost records; confirms individual records are maintained by state registries, not the CDC.. 3. Look through personal documents at home: paper shot cards, school files, military records.

Many people find at least a partial record that reduces what needs to be tested. If records are confirmed lost, bring a list of vaccines you believe you received, your date of birth, and the names of any institutions that may have kept a copy.

Step-by-step: getting titers ordered and documented

Step 1. Contact your primary care provider or an urgent care clinic and explain that you need titer testing to document immunity.

Step 2. The clinician reviews your history and orders a blood draw for the appropriate panels.

Step 3. Results are typically available within a few days to about a week.

Step 4. Your provider gives you a lab report with interpretation that you can submit to a school, employer, or licensing board.

Step 5. If any titer comes back non-immune, your provider recommends the relevant vaccine — and can often administer it at the same visit.

Special situations that change the picture

Healthcare workers and students face the most rigorous documentation requirements. Hospital occupational health programs often run a standardized titer panel and may cover the cost.

People born before 1957 are generally considered immune to measles, mumps, and rubella based on presumed natural exposure; many institutions do not require a titer for this group 1Ref 1Wodi AP, Issa AN, Moser CA, Cineas S (2025).Advisory Committee on Immunization Practices Recommended Immunization Schedule for Adults Aged 19 Years or Older — United States, 2025.Serologic evidence of immunity as acceptable alternative to documented vaccination; guidance on pre-1957 birth-year presumptive immunity; re-vaccination safety; ACIP recognition of titers for MMR, varicella, hepatitis B..

Immunocompromising conditions or medications — organ transplant recipients, people on high-dose biologics or corticosteroids — may not mount a detectable antibody response even after vaccination. Interpreting titer results in this population requires specialist input.

Cost and insurance — titer panels can range from modestly priced to several hundred dollars depending on how many diseases are tested. Employer or school reimbursement is sometimes available; check before paying out of pocket.