Interventions for Tuberculosis Control and Elimination 2002

Prospective and retrospective studies on BCG vaccination
In one of the first clinical trials with a methodologically fairly acceptable
design (systematic alternate allocation), BCG was given to children exposed
to a parent with tuberculosis and compared to a similar group who did not
receive the vaccine. 736 The impact on fatality was dramatic, with an 82%
reduction in the risk (figure 59). Nevertheless, suspicion about the efficacy
of BCG vaccination persisted, particularly in the United States, 737 but
also in the United Kingdom, 679 largely because the design of many studies
was dubious at best.
One of the most conspicuous differences observed in the protection
afforded by BCG reveals that age at vaccination is important. Of further
crucial importance is the type of tuberculosis that is targeted for protection
by vaccination.
In the following summary of the best-known studies in the English literature,
the studies are identified as being prospective or retrospective. For
each of these two study types five classes were examined:
• protection against disseminated and meningeal tuberculosis, and against
death from tuberculosis;
• protection afforded to children by vaccination of newborns or infants;
• protection afforded by vaccinating children beyond the age of one year;
Per cent with fatal outcome
12
10
8
6
4
2
0
10 of 84
All due to
miliary TB
107
1 of 41
Pulmonary
tuberculosis
Controls Vaccinated
Reduction: 81.5%
Figure 59. Comparative case fatality from tuberculosis among newborns vaccinated
and not vaccinated with BCG in a clinical trial with systematic assignment to
the experimental or control arm. 736