Should medical students be routinely offered BCG vaccination?

To the Editor: We disagree with the recent recommendation of Graham and colleagues that all medical students should be offered BCG vaccination.1 In countries with a low prevalence of tuberculosis (TB), the side effects from the vaccine and losing the use of a Mantoux test to readily diagnose recent TB infection outweigh any benefits of a vaccine with relatively poor efficacy.

The incidence of pulmonary TB in Australia is low (3.3 per 100 000 per year) and only 1.5% of isolates are multidrug-resistant.2,3 Thus, the likely exposure of medical students and doctors in Australia to pulmonary TB (let alone multidrug-resistant TB) will be low. In addition, most hospitalised patients with pulmonary TB would have been suspected of having TB before being sent to hospital, so adequate respiratory precautions should have been in place for most. This makes the risk of transmission to health care workers very small.

Information from the Australian immunisation handbook is also very relevant to this debate.4 BCG can be effective, but mainly in preventing disseminated TB in children (> 80% efficacy). In adults, the overall protective efficacy is only about 50%,4 and the sole Australian study showed, at best, a protective efficacy of only 30%.5 The effect of BCG may not persist for more than 10 years but repeat vaccination is not recommended.4

Adverse events occur in about 5% of those vaccinated, with 2.5% being injection site abscesses and 1% lymphadenitis. About 1% of vaccinees may need medical attention as a result of the adverse event. Anaphylactoid reactions can occur, and keloid scarring can also occur (although rarely) at the injection site. The vaccine is “live”, and therefore contraindicated in anyone who might have HIV, other forms of immunosuppression, or generalised skin diseases.4

Graham and colleagues believe the problem of BCG vaccination interfering with the interpretation of Mantoux results can be overcome by using whole blood-based interferon assays, such as QuantiFERON-TB Gold, purportedly unaffected by BCG vaccination.1 However, the data for QuantiFERON-TB Gold need to be treated with some caution because it is a new test and there is no gold standard against which to compare it for diagnosing latent TB. The specificity of interferon assays in diagnosing latent TB has been estimated at 95% or more,6 but this will still result in a poor positive predictive value if the pretest probability of latent TB infection is low — and this is the case for health care workers in Australia.

In summary, Australia is far more likely to protect its health care workers from TB through effective hospital infection control measures and migrant screening than through a vaccination program with a mediocre vaccine.