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TB Notes 2, 2003

Timing of Tuberculosis Testing and Smallpox Vaccination

An important issue has been raised recently by some of our partners in various TB control programs, i.e., the timing of the administration of the tuberculin skin test and the smallpox vaccine. Some of the persons currently being targeted for vaccination against smallpox intersect populations in whom CDC recommends annual tuberculin skin testing (TST), such as health care workers.1,2 In 2000, guidance was given on this subject in the document entitled “Diagnostic standards and classification of tuberculosis in adults and children3":

Vaccination with live-attenuated virus can cause suppression of the PPD response in patients known to be infected with M. tuberculosis. Live-attenuated vaccines that may cause false-negative PPD results are measles, mumps, rubella, oral polio, varicella, yellow fever, BCG, and oral typhoid. This suppression does not appear within the first 48 h after measles vaccination, so the Advisory Committee on Immunization Practices recommends that tuberculin testing be done either on the same day as vaccination with live virus or 4-6 wk later.4-7

A recent MMWR Recommendations and Reports article offers smallpox-specific guidance, with inclusion of a more current reference to CDC immunization guidelines2:

Suppression of tuberculin skin test (purified protein derivative [PPD]) reactivity has been demonstrated after administration of smallpox vaccine,8 as has been observed after administration of other parenteral live-virus vaccines.9 Health-care workers scheduled to receive an annual PPD skin test should not receive the skin test for 1 month after smallpox vaccination to prevent possible false-negative reactions.

Please call the DTBE duty officer with any questions at (404) 639-8140.

—Reported by Michael Iademarco, MD, MPH
Div of TB Elimination


1. CDC. Guidelines for preventing the transmission of Mycobacterium tuberculosis in health-care facilities, 1994. MMWR 1994;43 (No. RR-13).
2. CDC. Recommendations for using smallpox vaccine in a pre-event vaccination program. Supplemental recommendations of the Advisory Committee on Immunization Practices (ACIP) and the Healthcare Infection Control Practices Advisory Committee (HICPAC). MMWR 2003;52 (No. RR-7).
3. ATS/CDC. Diagnostic standards and classification of tuberculosis in adults and children. Am J Respir Crit Care Med 2000;161:1376-1395.
4. CDC. General recommendations on immunization: recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR 1994; 43 (No. RR-1):15.
5. CDC. Measles prevention: recommendations of the Immunization Practices Advisory Committee (ACIP). MMWR 1989; 38 (No. S-9):13.
6. American College of Physicians Task Force on Adult Immunization and Infectious Diseases Society of America. Guide for Adult Immunization, 3rd ed. Philadelphia, Pa: American College of Physicians; 1994.
7. American Academy of Pediatrics. Active and passive immunization. In: Peter G, ed. 1994 Red Book: Report of the Committee on Infectious Diseases, 23rd ed. Elk Grove Village, Illinois: American Academy of Pediatrics; 1994.
8. Smithwick EM, Steiner M, Quick JD. Vaccinia virus and tuberculin reactivity [Letter]. Pediatrics 1972;50:660-1.
9. CDC. General recommendations on immunization: recommendations of the Advisory Committee on Immunization Practices (ACIP) and the American Academy of Family Physicians (AAFP). MMWR 2002;51 (No. RR-2).


Released October 2008
Centers for Disease Control and Prevention
National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention
Division of Tuberculosis Elimination -

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