How long after receiving a live vaccine can I have a Tuberculin (TB) skin test?

Timing of TB Skin Test After Live Vaccine Administration

You should wait 4-6 weeks after receiving a live vaccine before administering a tuberculin skin test (TST), as live vaccines can temporarily suppress tuberculin reactivity and cause false-negative results. 1

Recommended Timing

• The optimal approach is to perform the TB skin test on the same day as the live vaccine administration, then read it 48-72 hours later, before any vaccine-induced immunosuppression occurs 1
• If the TB skin test was not done on the day of vaccination, wait 4-6 weeks after measles vaccination (or other live vaccines) before administering the TST 1
• This 4-6 week waiting period allows the temporary suppression of tuberculin reactivity caused by live viral vaccines to resolve 1

Why This Timing Matters

• Live measles vaccine (and other live viral vaccines) can temporarily suppress delayed-type hypersensitivity reactions, including the tuberculin skin test response 1
• This immunosuppression begins shortly after vaccination and can persist for 4-6 weeks 1
• Testing during this window period may produce false-negative results, potentially missing true tuberculosis infection 1

Alternative Evidence on Simultaneous Testing

• One research study from 1975 found that simultaneous administration of tuberculin testing with measles, mumps, or rubella vaccines did not significantly invalidate the test results in children already known to be tuberculin-positive 2
• However, this contradicts the established guideline recommendation and involved a unique population (children already known to be tuberculin-positive from prior BCG vaccination), making it less applicable to routine screening 2
• The guideline recommendation from the Immunization Practices Advisory Committee remains the standard of care and should be followed in clinical practice 1

Clinical Algorithm for Decision-Making

If you need both a live vaccine and TB screening:

1. Best option: Administer the TB skin test on the same day as the live vaccine, read 48-72 hours later 1
2. If TB test not done same day: Wait 4-6 weeks after live vaccine before placing the TB skin test 1
3. If TB testing is urgent and cannot wait: Consider using an interferon-gamma release assay (IGRA) instead, as these are not affected by live vaccines 3, 4

Common Pitfalls to Avoid

• Do not administer a TB skin test 1-4 weeks after a live vaccine, as this is the peak period of vaccine-induced immunosuppression and will likely yield false-negative results 1
• Do not delay necessary live vaccines to perform TB testing first unless there is high clinical suspicion for active tuberculosis requiring immediate evaluation 1
• Do not confuse this timing with the 8-10 week window period for TB exposure, which is a completely different concept related to the time needed for the immune system to mount a detectable response after M. tuberculosis exposure 1, 5