Dear Colleague Letters

COVID mRNA vaccines, TST, and IGRA – Follow-up

August 31, 2021

Dear Colleagues:

On January 7, 2021, we sent out a Dear Colleague letter about the timing of COVID-19 mRNA vaccinations and the immune-based tests for M. tuberculosis infection, that is, the tuberculin skin test (TST) and interferon gamma release assays (IGRAs). At that time, we were responding to questions as to whether the new COVID-19 mRNA vaccines could change the results from those tests. To date, no studies of TST or IGRA results after COVID-19 vaccination have been published. Of what is known about the immunologic response to COVID-19 mRNA vaccination, nothing would be expected to change TST or IGRA results.

As of today, August 31, 2021, CDC is posting new recommendations about COVID-19 vaccination and the timing of immune-based tests for tuberculosis infection, such as the TST and IGRA, on its COVID-19 website (at

“COVID-19 vaccination should not be delayed because of testing for TB infection. Testing for TB infection with one of the immune-based methods, either the tuberculin skin test (TST) or an interferon release assay (IGRA), can be done before, after, or during the same encounter as COVID-19 vaccination.

“TSTs and IGRAs were previously recommended to be administered > 4 weeks after completion of COVID-19 vaccination to minimize potential interference between vaccination and TB testing. This was out of an abundance of caution during a period when these vaccines were new. However, given logistical challenges faced in delaying TB infection testing, the recommendation has been updated so that these tests may now be administered without regard to timing of COVID-19 vaccination.”

Patients who have active TB disease or an illness that is being evaluated as active TB disease can receive a COVID-19 vaccine (note: the presence of a moderate or severe acute illness is a precaution to administration of all vaccines).

Thank you for your continued hard work in the COVID-19 response, and in all that you do to continue to prevent and control TB.



Terry Chorba
Terence Chorba, MD, DSc
Chief, Field Services Branch, Division of Tuberculosis Elimination
National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention
Centers for Disease Control and Prevention
1600 Clifton Road NE (US 12-4), Atlanta, GA 30329