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Year : 2023  |  Volume : 12  |  Issue : 1  |  Page : 43-48

Epidemiology of the koch phenomenon of infants after bacillus calmette–Guerin vaccination by interferon-γ release assay status, Japan, 2013–2019

1 Division of Technical Assistance to National Tuberculosis Programmes, Research Institute of Tuberculosis, Tokyo, Japan
2 Department of Paediatrics, Yamanashi Red Cross Hospital, Yamanashi, Japan

Correspondence Address:
Masaki Ota
No. 3-1-24 Matsuyama, Kiyose 204-8533, Tokyo
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ijmy.ijmy_203_22

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Background: The epidemiology of infants who exhibited the Koch-like phenomenon after Bacillus Calmette–Guérin vaccination and who subsequently tested positive in interferon-γ release assay (IGRA) was compared to that of those who tested negative. The reports of pediatricians on the phenomenon to the health authorities of Japan were retrieved and analyzed. Methods: In 2013–2019, 790 infants with such events were reported with IGRA test results available, of whom 81 (10.3%) tested positive and 709 (89.7%) negative. Results: The infants who were IGRA positive did not show an increasing trend (P = 0.06, P = 0.60), whereas those who were IGRA negative showed a significantly increasing trend (P = 0.42, P = 0.0002). The infants who were IGRA positive did not exhibit seasonality, whereas those who were IGRA negative had a higher number of cases in winter than in summer. The rates of infants who were IGRA positive per 10 million live births showed a significant correlation with the tuberculosis (TB) notification rates by prefecture (P = 0.41, P = 0.004), whereas those who were IGRA negative did not (P = 0.04, P = 0.78). Conclusion: The IGRA-positive infants were distributed quite differently from those who were IGRA negative and appeared more likely to be infected with TB. Reports of pediatricians on the Koch-like phenomenon should continuously be collected as the reports reflect a risk of TB infection including TB outbreaks among infants in Japan. The reports should include IGRA test results as IGRA is more specific than tuberculin skin testing. Infants with IGRA-positive results should be followed up for 2–3 years to determine their final outcomes.

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