This paper explores how criticism surrounding the ethics and safety of biomedical technologies circulates and 'converts' through global-local religious encounters, producing new claims of moral opposition and rights to religious freedom. The paper is concerned with the question of what rhetorical devices make vaccine safety doubt relevant to religiously Orthodox settings and what implications arise? Based on an ethnographic study of vaccine decision-making and non-vaccination advocacy in Jerusalem, the paper examines how opposition is forged amidst evolving global-local encounters and relations. The data reveal how Christian activists attempt to engender ethical and moral opposition to vaccination among American Orthodox Jews in Jerusalem by 'converting' public criticism around safety into a religious discourse of bodily governance. Pinpointing how critiques of biomedical technologies discursively 'convert' offers a conceptual template in anthropology to chart how counter-positions are formed and transformed amidst evolving tensions between biomedical and religious cosmologies.