Volume 186 - Issue 2
Should medical students be routinely offered BCG vaccination?
Authors: Maryza Graham, Tanya M Howley, Robert J Pierce and Paul D R Johnson
Med J Aust 2007; 186 (2): 98-99. || doi: 10.5694/j.1326-5377.2007.tb00816.x
Published online: 15 January 2007
Published online: 15 January 2007
In reply: The intention of our article was to highlight inconsistent approaches to tuberculosis (TB) prevention in Australian medical schools and stimulate a new informed debate. We therefore welcome the responses from Senanayake and Collignon, and Durrheim and Hensley.
Interference with interpretation of tuberculin skin testing (TST) is one argument cited against the use of BCG vaccination for health care workers. While we agree that the new blood-based tests need further evaluation, unlike TST, they are not affected by BCG because they employ TB-specific antigens. The lack of a gold standard for diagnosis of latent TB affects both TST and the blood-based tests. Recent reviews of these new tests have been favourable — including one that states that, compared with TST, these new assays seem to have “better correlation with surrogate measures of exposure to M. tuberculosis” and that “because of their higher specificity they may be helpful in low-prevalence, resource-rich settings where cross-reactivity due to BCG may pose difficulty in BCG interpretation”.1 In fact, this article summarised the specificity of these new tests as between 95% and 100%. Other authors found a specificity of 98.1%.2
We agree that infection control is crucial in preventing nosocomial TB transmission, but every infection control practitioner has seen patients with unrecognised TB admitted to an open ward. One missed patient can mean contact-tracing and testing of dozens of staff. The Melbourne Mantoux study (involving 14 Melbourne hospitals) found that health care work and years of hospital employment were significantly associated with a positive Mantoux result — indicating the risk to Australian health care workers is not “negligible” as Durrheim and Hensley state. Nosocomial outbreaks of TB are well documented in low-prevalence countries.1,3
BCG is by no means a perfect vaccine. However, while BCG efficacy was once thought to only last 10 years, a recent large study suggested that it persists for 50–60 years,4 and there is new evidence that BCG vaccination may prevent some primary infections.5 While the risk of health care-associated tuberculosis in Australia is currently low, it would be unwise to assume this will remain the case, or that doctors will only work in safe environments. What will be the effects of HIV, further immigration from high-risk countries, drug resistance and the increasing use of immunosuppressant medications on the incidence of TB? We stand by the recommendations in our article, although we acknowledge they are controversial. There should, however, be no controversy about the need for a consistent policy concerning TB prevention in our medical schools.
References
- Silva VM, Cunha AJ, Kritski AL. Tuberculin skin test conversion among medical students at a teaching hospital in Rio de Janeiro, Brazil. Infect Control Hosp Epidemiol 2002; 23: 591-594. 0_CBBHJIDJ
- Mori T, Sakatani M, Yamagishi F, et al. Specific detection of tuberculosis infection: an interferon-gamma-based assay using new antigens. Am J Respir Crit Care Med 2004; 170: 59-64. 0_CBBGADFH
- Menzies D, Fanning A, Yuan L, FitzGerald JM. Hospital ventilation and risk for tuberculous infection in Canadian health care workers. Canadian Collaborative Group in Nosocomial Transmission of TB. Ann Intern Med 2000; 133: 779-789. 0_CBBIHAJG
- Aronson NE, Santosham M, Comstock GW, et al. Long-term efficacy of BCG vaccine in American Indians and Alaska Natives: a 60-year follow-up study. JAMA 2004; 291: 2086-2091. 0_pgfId-1163131
- Soysal A, Millington KA, Bakir M, et al. Effect of BCG vaccination on risk of Mycobacterium tuberculosis infection in children with household tuberculosis contact: a prospective community-based study. Lancet 2005; 366: 1443-1451. 0_i1091803