Should medical students be routinely offered BCG vaccination?

Young adults who initially have negative tuberculin skin test (TST) results but have subsequent positive TST results have a relatively high rate of early progression to clinical tuberculosis (TB),1 and the estimated lifetime risk of developing pulmonary TB is highest after infection in early adulthood — around 15% for those infected at age 20 years.2 In Box 1, we describe a medical student who may have developed symptomatic pulmonary tuberculosis during her intern year had her infection not been detected early by her university screening program. However, might TB have been prevented if she had received BCG vaccine at medical school?

Until recently, all medical students in Victoria were routinely screened with TSTs, and those with negative results were offered BCG vaccine. Melbourne University stopped this practice in 1996 and Monash University stopped it in 2000.

The 2003 Australian immunisation handbook makes no clear statement about BCG for health care workers, stating that “State and Territory guidelines should be consulted”.3 The 2002 Victorian Department of Human Services guidelines advise that BCG may be considered in health care workers who have a high risk of occupational exposure to TB, who are TST-negative, and who are likely to be exposed to active cases of multidrug-resistant TB (MDR-TB).4

In the absence of definitive national and state guidelines covering medical students, the Committee of Deans of Australian Medical Schools developed their own guidelines in 2003. The document states that BCG vaccination is not required in students with a negative TST result, but that this recommendation is not universally accepted and medical schools may choose to include this recommendation within their programs.5

Current practice in Australia’s 15 medical schools varies widely (see Box 2). We contacted all Australian medical schools and found that all except one recommend a baseline TST early during the medical course, one also offers an “exit” TST to medical students before graduation, four schools recommend the BCG vaccine to all medical students with a negative TST result, and one offers the BCG vaccine, but the uptake rate is variable; the remaining medical schools do not routinely recommend BCG vaccine.

Health care workers can be exposed to TB in Australian hospitals,6,7 although the risk is clearly higher if they work overseas. For example, the risk of TB infection in long-term Dutch travellers to high-endemicity countries was 2.8 per 1000 person-months of travel (3.3% per year), after excluding health care workers. However, for health care workers who worked overseas in patient care, the rate was 9.8 per 1000 person-months of travel (12% per year).8 In a low-incidence setting comparable with Australia (Germany), culture-positive isolates over a 6-year period were genotyped as well as contact-traced. Epidemiological analysis showed that recent transmission was strongly associated with health care work.9

One strategy for preventing tuberculosis in health care workers who plan to work in a high-risk situation is serial TSTs, with post-exposure prophylaxis for those whose TST results convert from negative to positive. Prophylaxis with isoniazid carries the risk of side effects. The most serious of these is hepatitis; the risk of developing hepatitis increases dramatically with age, but is about 0.3% in those aged 20–34 years.10 Furthermore, TST ideally involves a two-step protocol before departing for a TB-endemic area (to detect the booster phenomena), and retesting at 2–3 months after returning. This would involve six visits to health care providers experienced in giving and interpreting the TST for one period of overseas work. Several studies have shown that compliance with this recommendation is poor, even for only one pre-travel and one post-travel TST (four visits). For travellers, compliance rates of around 61% have been reported, with 33% of the compliant travellers requiring extra phonecalls.8,11 Among physicians, adherence rates for TSTs vary from 30% to 72% in North American studies.12

MDR-TB is defined as resistance to both isoniazid and rifampicin, and is uncommon in Australia (1%–2% of bacteriologically confirmed isolates over the decade to 2003).13 Rates in south-east Asia range from 2%–7%, and are higher in some provinces of China.14 The proportion of MDR-TB cases in Lesotho, South Africa (where the medical student whose case we describe worked), was less than 2% in 1994, but, because of the high incidence of TB, this translated to an estimated 105 new cases of MDR-TB that year.15 BCG vaccine can protect against MDR-TB (as well as sensitive TB), but TST screening with post-exposure prophylaxis cannot.

Given the risks of TB infection, why is BCG vaccine no longer routinely offered to medical students? Arguments include concerns about its efficacy, safety and potential to interfere with interpretation of the TST.16-19

Australia has one of the lowest rates of TB in the world, but exposure to TB remains an occupational hazard for Australian health care workers.6 We acknowledge that BCG vaccination is not perfect, but it is cheap and safe, provides reasonable long-lasting protection — including from MDR-TB — and only one dose is required. Until more definitive data become available, we propose a standard approach for all Australian medical schools that incorporates offering BCG vaccination to all students who test negative to tuberculin skin and TB blood testing (see Box 3).