How Does Titer Testing Work?

A titer test is a blood test that measures the concentration of antibodies against a specific pathogen. Antibodies are proteins produced by your immune system in response to vaccination or natural infection. A sufficient level of antibodies (a "positive" or "protective" titer) indicates that your immune system has been primed to fight that disease.

The blood sample is drawn at the civil surgeon's office and sent to a USCIS-approved laboratory. Results are typically available within a few days.

Which Vaccines Can Be Verified by Titer Testing?

Titer testing is available and accepted for the following immigration-required vaccines:

• Measles (rubeola) — IgG antibody titer
• Mumps — IgG antibody titer
• Rubella — IgG antibody titer
• Varicella (chickenpox) — IgG antibody titer
• Hepatitis B — hepatitis B surface antibody (anti-HBs)
• Hepatitis A — hepatitis A IgG antibody

Which Vaccines Cannot Be Verified by Titer Testing?

Titer testing is not a reliable or accepted method for verifying immunity to the following vaccines:

• Td/Tdap (tetanus, diphtheria, pertussis) — no reliable titer test; vaccination required
• Meningococcal vaccines — no reliable titer test; vaccination required
• Pneumococcal vaccines — no reliable titer test; vaccination required
• Influenza — annual vaccination required; titers not used
• COVID-19 — vaccination required; titers not accepted

What Happens If My Titer Is Positive?

If your titer result is positive (protective), the civil surgeon will document the positive titer on Form I-693 as evidence of immunity. You do not need to receive that vaccine again. The positive titer satisfies the vaccination requirement for that disease.

What Happens If My Titer Is Negative?

If your titer result is negative (non-protective), you are not considered immune to that disease and will need to receive the vaccine. After vaccination, a repeat titer is generally not required — the vaccination itself satisfies the requirement.

In some cases, a single dose of vaccine may not produce a protective titer response. The civil surgeon will follow the recommended vaccination schedule for that vaccine, which may include a second dose or booster.