Tensions and opportunities in the roles of senior public health officials in Canada: A qualitative study

•Chief Medical Officers of Health variously act as advisors, managers, and communicators.•As public servants, tensions exist between their government- and public-facing roles.•Officials use political acumen and pragmatism to navigate these tensions.•The role's design differs across jurisdictions and affects incumbents’ pathways to impact.•When designing the role, governments must balance trade-offs and consider desired outcomes.