TST and tuberculosis: Another study in Vietnam showed 25.8% TST ⩾10 mm positivity among contacts of new TB patients and 40.8% among contacts of multidrug-resistant TB (MDR-TB) patients.18 In 2020, the Vietnam NTP implemented community campaigns using a different ­tuberculin reagent (BulBio, BB-NCIPD Ltd, Sofia, Bulgaria) than the prevalence survey.