The influence of BCG immunisation on tuberculin reactivity and booster effect in adults in a country with a high prevalence of tuberculosis

Abstract

The relationship of age and previous BCG vaccination with tuberculin skin test (TST) reactivity was investigated to assess the interpretation of TST results in the adult population of Turkey, where there is a high prevalence of tuberculosis and a routine BCG vaccination programme. The influences of age and BCG vaccine status on booster reaction were also evaluated. TST was applied (5 tuberculin units of purified protein derivative intradermally) to two healthy adult groups, namely 98 medical students and 187 elderly people in a retirement home. The TST was considered positive if an induration > or = 10 mm in diameter was produced. Subjects (41 elderly people and 39 students) with a reaction < 10 mm in diameter were retested 1 week later. There was no significant difference between the students (59.1%) and elderly subjects (58.8%) with respect to positive TST response. No influence of BCG scars on TST reactivity was observed in either group. The booster effect was seen more commonly in the elderly, but the presence of a BCG scar did not influence the booster effect in either group. It was concluded that a positive TST response and booster reaction in adults in high-prevalence countries may be caused by latent tuberculosis rather than previous vaccination.

Correlates ofMycobacterium tuberculosisinfection in a prison population

“…In Italy, BCG became mandatory by law for certain risk groups and all military recruits starting in 1970, and was routinely performed up to 2002. The influence of BCG on TST results is low in subjects from countries with a high TB prevalence [42]. For all the previous reasons, if any influence of BCG on the current authors' TST was suspected, it would have led to an overestimation of the MT infection, mainly among the younger inmates and those born in Italy; even if this overestimation had been recognised, it would have strengthened, rather than weakened, the strong correlation found between TST reactivity and both older age and being foreign-born.…”

“…However, if a previous BCG vaccination ever influenced the overall prevalence of positive TST, it is believed that this occurred only to a minor extent, and that this possible influence did not significantly affect the identification of the correlates of the MT infection. In fact, several recent studies found no significant effect of a previous BCG on TST results [42][43][44], since BCG reactivity disappears within years [44]. A metaanalysis on this topic showed that this reactivity becomes either very weak or absent within 15 yrs of vaccination [45].…”

“…A metaanalysis on this topic showed that this reactivity becomes either very weak or absent within 15 yrs of vaccination [45]. BCG was incorporated into the infant vaccination schedule by the Expanded Programme on Immunization in 1974 [42], but the coverage in many countries remained inadequate for o10 yrs [46]. BCG was prescribed and administered at birth or within the fifth year of age in most countries [47].…”

Risk of tuberculosis in patients treated with tumor necrosis factor antagonists due to incomplete prevention of reactivation of latent infection

“…Furthermore, the effect of BCG vaccination on positive TST in adults ages Ͼ30 years is probably negligible (16). Also, in countries with a high prevalence of tuberculosis, positive TST response and positive retest in adults is caused by latent tuberculosis rather than previous vaccination (17). All in all, TST and TST retest seem to be valuable tools for evaluation of tuberculosis in countries with a high prevalence rate of ATB.…”

Resposta de testes de hipersensibilidade tardia utilizando PPD e outros antígenos em crianças e adolescentes saudáveis e infectados pelo HIV-1 e vacinados com BCG

“…Some studies have shown that PPD reactivity in BCG-vaccinated individuals wanes with time 13 , suggesting that environmental exposure to mycobacteria may be crucial to maintain PPD reactivity 7,14 . In our study, both natural environmental exposure to mycobacteria and BCG vaccination may have played a synergistic role to sustain PPD reactivity among immunocompetent healthy children and adolescents, regardless of their age 15,16 .…”