What Titer Tests Measure

A titer test is a blood test that measures the concentration of specific antibodies in your bloodstream. Antibodies are proteins produced by your immune system in response to infection or vaccination. The presence of sufficient antibodies indicates that your immune system is prepared to fight off a specific disease — a state called immunity.

Titer results are reported as a numerical value or ratio (the "titer") that reflects the concentration of antibodies detected. Results above a defined threshold are considered positive, or immune. Results below the threshold are considered negative, or non-immune, indicating that your body may not have adequate protection against that disease.

What a Positive (Immune) Titer Result Means

A positive titer result — also called a reactive or immune result — means that your blood contains a sufficient level of antibodies to indicate immunity to the disease being tested. This immunity may have developed through prior vaccination, prior infection, or both. A positive titer result is considered evidence of immunity for immigration purposes.

If your titer result is positive for a particular disease, you do not need to receive the corresponding vaccine as part of your immigration medical exam. The civil surgeon will document the positive titer result on Form I-693 as evidence of immunity, and no additional action is required for that disease.

What a Negative (Non-Immune) Titer Result Means

A negative titer result — also called a non-reactive or non-immune result — means that your blood does not contain a sufficient level of antibodies to indicate immunity. This may mean you were never vaccinated, that your prior vaccination did not produce a lasting immune response, or that immunity has waned over time.

If your titer result is negative for a disease that is on the USCIS vaccination requirement list, you will need to receive the corresponding vaccine before Form I-693 can be completed. Our clinic offers on-site vaccinations, so in most cases you can receive the required vaccine during the same visit or at a follow-up appointment.

Which Vaccines May Require Titer Testing

Titer tests are most commonly ordered for the following vaccine-preventable diseases in the immigration medical examination context:

• Measles, Mumps, and Rubella (MMR) — titer testing is commonly used to verify immunity, particularly for adults who received older vaccine formulations
• Varicella (chickenpox) — a positive titer confirms immunity from prior infection or vaccination
• Hepatitis B — titer testing may be used to confirm immunity from prior vaccination series
• Hepatitis A — titer testing may be ordered in certain circumstances

How Titer Results Affect Your Vaccine Requirements

The USCIS vaccination requirements for immigration are based on the CDC's Advisory Committee on Immunization Practices (ACIP) schedule. For each required vaccine, the civil surgeon must document either proof of prior vaccination (vaccination records) or serologic evidence of immunity (a positive titer). If neither is available, the vaccine must be administered.

Titer testing is particularly useful when you do not have vaccination records available. Rather than receiving vaccines you may have already had, a positive titer result can serve as documentation of immunity and eliminate the need for re-vaccination. This can save time and reduce the number of injections required during your exam.

Timing and Results for Titer Tests

Titer tests are performed via blood draw on the day of your immigration medical exam. Results are typically available within two to four business days, depending on the specific tests ordered. If your titer results are positive, no further action is needed for those diseases. If results are negative, our staff will contact you to schedule the required vaccinations.

In some cases, the civil surgeon may order titer tests at a preliminary appointment before your full exam, so that vaccination needs are known in advance and vaccines can be administered during the main exam visit. Our staff will advise you on the most efficient approach for your situation.