Timing of TB Skin Test After Live Vaccine Administration

Recommended Timing

The Centers for Disease Control and Prevention recommends waiting 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
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, it is recommended to wait 4-6 weeks after measles vaccination (or other live vaccines) before administering the TST 1

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

If you need both a live vaccine and TB screening, the best option is to administer the TB skin test on the same day as the live vaccine, read 48-72 hours later 1
If TB test not done same day, it is recommended to wait 4-6 weeks after live vaccine before placing the TB skin test 1
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 2, 3

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 4, 5

The CDC recommends administering the TST and the measles‑mumps‑rubella (MMR) vaccine on the same day and reading the TST 48–72 hours later, before any vaccine‑induced immunosuppression can affect the result, thereby providing immediate measles protection while preserving TST accuracy. 6

If the MMR vaccine was administered previously, the CDC advises waiting at least 4 weeks (preferably 4–6 weeks) before placing the TST to avoid transient suppression of delayed‑type hypersensitivity. This recommendation is supported by both the 2006 and 1998 CDC MMWR reports. [6][7]

Live‑attenuated measles vaccine can transiently suppress delayed‑type hypersensitivity reactions, leading to false‑negative TST results when testing occurs during the suppression window. [6][7]
The suppression may begin shortly after vaccination and can persist for 4–6 weeks, with the highest risk of false‑negative results during the 1–4‑week period post‑vaccination. [6][7]

The same timing principles apply to other live‑attenuated viral vaccines, including varicella, yellow fever, and smallpox (the latter explicitly requires a 4‑week delay before TST). In the absence of vaccine‑specific data, the CDC recommends following the measles‑vaccine guidance as a prudent approach. 6

If a TST is inadvertently placed during the immunosuppressive window, the CDC advises repeating the test after the appropriate interval (i.e., after ≥4 weeks from vaccination). 6

Individuals with untreated active tuberculosis should receive antituberculosis therapy before receiving MMR, because measles vaccination could theoretically exacerbate the disease. 6
A positive TST (in the absence of active disease) is not a contraindication to MMR vaccination. 6