Dr. Nardell emphasized that much of the clinical disease
attributed to reactivation of latent infection in high exposure settings
is likely to be due to exogenous reinfection, as shown by studies
done in the high burden settings of homeless shelters [6] and gold
mines [7]. Exogenous reinfection is an alternative pathway versus
endogenous reactivation to cavitary TB, and continuous ongoing
transmission, repeated exposure and reinfection in high burden
settings represents a major obstacle to tuberculosis control [8,9].
Studies of reinfection suggest that prior TB disease is a risk factor
for reinfection, with recurrence rates found to be much higher
than incidence rates for new TB infections [10–12]. Accordingly,
developing a vaccine capable of preventing the establishment of
sustained Mtb infection, thereby eliminating the cycle of infection
leading to disease and increased susceptibility to re-infection among those who become infected with Mtb, would represent a
major contribution to Mtb control efforts.