Mycobacterium Infections Nontuberculous

The purpose of this study is to find out if the Mycobacterium bovis Bacillus Calmette Guerin (BCG) vaccine can be used safely to treat Mycobacterium avium complex (MAC) lung disease. Researchers will compare responses from patients with MAC lung disease after receiving an injection of BCG or placebo (a look-alike substance that contains no drug) Participants in the study: * Receive a BCG or placebo injection at UVA study center on Day 0 * Come to UVA study center on Day 60 * Come to UVA study center at the end of the study * Answer surveys and questionnaires about how you are doing * Have blood drawn 3 times, on injection day, day 60, and at end of study * Give the study team personal and demographic information * Discuss any new symptoms with the study team * Provide monthly sputum samples per usual care

This is a prospective observational study using whole genome sequencing (WGS) to investigate whether new strains (other than the initially identified strain(s)) of M. avium are responsible for persistently culture positive sputum during treatment (refractory disease), or the reversion to culture positive sputum after prior conversion to negative. The study will further investigate for differences between participants living in the Toronto/York region versus participants living elsewhere. The primary goal of this prospective observational study is to understand why some patients with M. avium lung disease have persistent or recurrent M. avium in their sputum despite treatment. The aim is to understand whether it is usually due to treatment failure or new infection.