Just as the COVID-19 pandemic has laid bare the limitations of medical codes of ethics (London 2021), it has also laid bare the limitations of scientific codes of ethics, particularly with regard to expert communication. This commentary will argue that scientific experts may face a fundamental dilemma between prioritizing actionability and prioritizing scientific transparency in their communications, and moreover, that this dilemma has an ethical dimension that should be anticipated in ethical guidelines for scientists.The crux of the trade-off facing scientific experts is the following. If the expert prioritizes actionability by downplaying scientific uncertainty, this can indeed spur the public to make behavioral changes. However, if the expert's statements turn out to be wrong afterwards, the trustworthiness of the scientist and indeed of the scientific community as a whole may suffer. The risk is that the public perceives experts to be paternalistic, where not all scientific details are communicated in order to avoid undesirable patterns of behavior. London's example of Dwayne "The Rock" Johnson, who communicated that "the plasma that's in your blood can literally save lives" (London 2021, 11), is a case in point of where actionability was prioritized over scientific transparency. Risks to future individual or collective trustworthiness may thus prevent a prudent scientific expert from prioritizing actionability too much over scientific transparency.Yet there is no easy way out, because a scientific expert can also be too scrupulous in conveying what the scientific community does not yet know or is not yet certain about. Newton once compared himself to a child collecting pebbles on the beach, at the edge of a great ocean of truth yet to be discovered. A similar epistemic humility from a scientific expert would not only lead to the expert being ignored in the crowded space of punditry and social media, it would also not help in persuading the public and policy-makers to change courses of action, especially when these involve costly mitigation measures such as has been the case in the COVID-19 pandemic.The existence of this fundamental trade-off is not always recognized by those who claim to speak "in the name of science only". Yet even when, for instance, meteorologists provide actionable advice to the public, also they are making trade-offs between actionability and transparency. The trade-off is not felt acutely since the cost of wrongly forecasting the weather is usually not steep; however, the trade-off is vividly present when uncertain but potentially catastrophic scenarios threaten. These are moments when high-confidence scientific predictions are in great public demand but short supply by scientists. The public will want to know, as far as is possible, how much should be invested in costly mitigation measures. Experts are then faced with a trade-off between meeting the public's need for actionable advice (whether to embark on mitigation or not) versus communicating the uncertainty of the scientific stat...