Which antibodies should be checked to assess vaccine-related immunity in a patient who has received a vaccine, considering their immune status and medical history?

Which Antibodies to Check for Vaccine-Related Immunity

The specific antibodies to check depend entirely on which vaccine was administered, but for the most commonly assessed vaccines: measure anti-HBs for hepatitis B, anti-HAV IgG for hepatitis A, and anti-S IgG for COVID-19 in high-risk populations only—routine postvaccination testing is not recommended for most vaccines in immunocompetent individuals. 1

General Principle: Most Vaccines Do Not Require Routine Antibody Testing

• Immunocompetent adults and children who complete standard vaccine series do not need postvaccination serologic testing for most vaccines, as long-term protection is assumed even when antibody levels decline over time due to immune memory 1
• The CDC explicitly states that routine testing after vaccination is unnecessary for the general population for most vaccines 1

Hepatitis B Vaccine: The Most Commonly Tested

Who Should Be Tested (1-2 Months After Final Dose)

• Healthcare personnel and public safety workers with potential blood/body fluid exposure 1, 2
• Hemodialysis patients (current or anticipated future need) 1, 2
• HIV-infected persons and other immunocompromised individuals 1, 2
• Sexual and needle-sharing partners of HBsAg-positive persons 1
• Infants born to HBsAg-positive mothers 1

What to Measure

• Anti-HBs (antibody to hepatitis B surface antigen) using quantitative ELISA 1, 2
• Anti-HBs ≥10 mIU/mL indicates protective immunity 1, 2
• Anti-HBs <10 mIU/mL requires revaccination with a complete 3-dose series, followed by repeat testing 1-2 months after completion 1

Special Considerations for Healthcare Workers Vaccinated in Childhood

• If anti-HBs <10 mIU/mL is found upon hire, give one booster dose and retest 1-2 months later 1
• If still <10 mIU/mL after booster, complete a second full 3-dose series and retest 1

Ongoing Monitoring

• Hemodialysis patients require annual anti-HBs testing with booster doses when levels decline to <10 mIU/mL 1, 2
• Immunocompromised persons may need annual anti-HBs testing 1

Hepatitis A Vaccine

• Anti-HAV total or IgG antibody should be measured 1-2 months after the second vaccine dose in high-risk populations (MSM, injection drug users, chronic liver disease patients, HBV/HCV co-infected individuals) 2
• A repeat vaccine series is recommended in those who remain seronegative 2
• Routine testing is not recommended for immunocompetent individuals 2

COVID-19 Vaccines

• Routine antibody testing after COVID-19 vaccination is NOT recommended for the general population 3
• Anti-S (spike protein) IgG antibodies can be measured if assessing vaccine response in research settings or high-risk immunocompromised patients 4, 5, 6, 7
• Anti-S IgG levels ≥10 mIU/mL correlate with neutralizing antibody activity and protection 6, 7
• Anti-N (nucleocapsid) antibodies distinguish natural infection from vaccination (only present after infection, not vaccination with mRNA or viral vector vaccines) 4

Influenza, Pneumococcal, and Other Routine Vaccines

• No routine antibody testing is recommended after influenza, pneumococcal (PCV13, PPSV23), HPV, zoster, MMR, varicella, Tdap, or meningococcal vaccines in immunocompetent individuals 2
• These vaccines are assumed to provide protection based on completion of the series 2

Tuberculosis Screening (Not a Vaccine Antibody Test)

• TST (tuberculin skin test) or IGRA (interferon-gamma release assay) should be performed at initiation of care for HIV-infected patients and those starting immunosuppressive therapy, but this tests for latent infection, not vaccine immunity 2

Common Pitfalls to Avoid

• Do not test anti-HBs in routine immunocompetent vaccinees years after vaccination—naturally waning antibody levels do not indicate loss of protection due to immune memory 1
• Do not restart the entire vaccine series for persons with low or undetectable antibodies—give a single booster dose first and retest 1
• Do not delay vaccination while waiting for serologic test results in at-risk individuals 1
• Do not confuse anti-HBc (core antibody) with anti-HBs (surface antibody)—anti-HBc indicates prior infection, while anti-HBs indicates immunity from vaccination or resolved infection 2
• Do not order antibody testing for vaccines where it is not clinically indicated—this creates unnecessary cost and patient anxiety 1

Algorithm for Decision-Making

1. Identify the vaccine in question
2. Assess patient's immune status: immunocompetent vs. immunocompromised
3. Determine occupational/exposure risk: healthcare worker, hemodialysis patient, HIV-infected, partner of HBsAg-positive person
4. If hepatitis B vaccine AND high-risk category: measure anti-HBs 1-2 months after final dose 1
5. If hepatitis A vaccine AND high-risk category: measure anti-HAV IgG 1-2 months after second dose 2
6. If any other routine vaccine in immunocompetent person: no testing needed 1
7. If immunocompromised: consider testing for hepatitis B (anti-HBs) and potentially hepatitis A (anti-HAV IgG), but not for other routine vaccines 1, 2