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Re: Re: Question for Flegg

http://bmj.bmjjournals.com/cgi/eletters/330/7483/112-d

BCG is a hodge-podge of attenuated mycobacteria strains. It is no doubt declining in overall efficacy as a vaccine, and there are intensive efforts underway to find better alternatives, which are sorely needed.

I do not recollect any studies where BCG being shown to be "worse than ineffective" in India. This may be what his favourite anti-vaccination web site claims, but a proper reference would be appreciated if it exists. Lucas may be referring to the TB Research Centre BCG trials in south India, which studied nearly two thirds of a million subjects (1).

In this trial, BCG was shown to be ineffective in preventing pulmonary tuberculosis in adults and it was of low efficacy in preventing TB in children. This is not quite the same thing as being “worse than ineffective”. Other recently reported long term trials have shown some protective efficacy against TB (2). BCG is still protective to a considerable degree against more invasive extra-pulmonary TB manifestations like meningitis and miliary TB, particularly in childhood, as demonstrated by at least two meta-analyses (3,4). BCG obviously has a very minor role to play in preventing transmission of TB as a public health measure, but it does reduce the complication rate and associated mortality.

Vaccine science can certainly have its mysteries, as Lucas refers to them, but the fact that some countries use different approaches to TB control is hardly surprising. There is logic behind the differing recommendations for BCG vaccination in different geographical regions, and this is mainly based on the epidemiology of TB. In areas with low TB prevalence such as the USA giving BCG is not felt to be beneficial. (Another reason is that in the USA, they prefer to use skin tests of reactivity to tuberculin for diagnostic purposes, and this is not feasible in patients who have had prior BCG). The UK saw a drop in cases of TB into the 1990s and phased out its BCG programme in response, but cases were already starting to rise at this time on the back of the burgeoning HIV epidemic and influx of people from high TB prevalence areas, hence the resumption of the programme (hiatuses in vaccine supply notwithstanding).

(1) http://www.trc-chennai.org/bcg1.pdf
(2) Aronson NE, Santosham M, Comstock GW, Howard RS, Moulton LH, Rhoades ER, and Harrison LH. Long-Term Efficacy of BCG Vaccine in American Indians and Alaska Natives: A 60-Year Follow-Up Study. JAMA. 2004:291 (17): 2086-91.
(3) Rodrigues LC; Diwan VK; Wheeler JG. Protective effect of BCG against tuberculous meningitis and miliary tuberculosis: a meta-analysis. Int J Epidemiol 1993 Dec;22(6):1154-8.
(4) Colditz GA; Brewer TF; Berkey CS; Wilson ME; Burdick E; Fineberg HV; Mosteller F. Efficacy of BCG vaccine in the prevention of tuberculosis. Meta-analysis of the published literature. JAMA 1994 Mar 2;271(9):698-702.

Competing interests: None declared