Uncertainty is inherent in new and unexpected viral outbreaks such as the current COVID-19 pandemic. It imposes challenges for health officials in soliciting cooperative behavioural changes based on incomplete information. In this paper, we use evolving mask recommendations in the United States as an example to analyse the ethical importance and practical demonstration of trustworthiness in pandemic messaging and decision-making. We argue that responsible public health interventions in the time of uncertainties requires explicit intersecting ethical considerations both in action and (...) in communication to promote trustworthiness. First, as public health decisions have to be made in the face of incomplete and evolving data, health officials need to exhibit competence while committing to epistemic humility. They can explain the methods used in making and updating mask recommendations as well as explicitly acknowledge the need to incorporate sociocultural and other contextual considerations in translating scientific data into mask recommendations. Second, officials and agencies must uphold and communicate decisional transparency as part of their effort to demonstrate accountability and promote the public’s understanding of the evolving pandemic. Third, especially since both the pandemic and mask recommendations may have disparate impact on different populations, officials should start with the fair implementation of the least restrictive measures that can help reduce harm. (shrink)