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TB Notes 2, 2003
Timing of Tuberculosis Testing and Smallpox
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
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.
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.
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.