Effect of BCG Vaccination on Childhood Tuberculosis in a Region with High Prevalence of Tuberculosis

Abstract

Introduction. BCG vaccination is included in the vaccination schedules of many countries. Numerous studies show its high efficacy, especially in regions with a high prevalence of the disease, and the limited efficacy of revaccination.The objective of the study: to estimate the occurrence of clinical forms of childhood tuberculosis (TB) depending on BCG vaccination in regions with a high prevalence of TB.Materials and Methods. The research design is a retrospective continuous comparative study. We analyzed the data of registration forms No. 089/y-tub of children aged 0 to 17 years with primary active tuberculosis (n = 450) over the period from 2017 to 2020 in Primorsky Territory. Children were divided into groups: 0-3 years old (n = 124), 4-6 (n = 88), 7-10 (n = 61), 11-14 (n = 75), and 15-17 (n = 102).Results. Contact with TB patients was a significant risk factor for children aged from 0 to 3 years.The study revealed a significant predominance of primary tuberculosis among non-BCG-vaccinated children aged 0 to 17 (60.7 and 84.2%, χ2 = 8.234, p = 0.005). Secondary tuberculosis prevailed in vaccinated children (32.3 and 5.6%, χ2 = 12.094, Pearson's contingency coefficient was 0.134 for primary forms and 0.162 for secondary forms).There were no significant differences between the generalized and extrapulmonary forms depending on the vaccination. At the same time, extrapulmonary forms were more common in unvaccinated children (4.9 and 10.5%, χ2 = 2.217, p = 0.137). Revaccination had no significant effect on the occurrence of clinical forms of TB.Conclusions. BCG vaccination has a protective effect against TB. The main preventive measures are early diagnosis of latent tuberculosis using a recombinant tuberculosis allergen skin test. Also, preventive therapy protects against endogenous and secondary TB. No convincing evidence of an additional protective effect of BCG revaccination was obtained.