In the initial phase of the COVID-19 pandemic, Sweden’s response stood out as an exception. For example, Sweden did not introduce any lockdowns, while many other countries did. In this paper I take the Swedish Corona Commission’s critique of the initial Swedish response as a point of departure for a general analysis of precaution in relation to pandemics. The Commission points out that in contrast to many other countries Sweden did not follow ‘the precautionary principle’. Based on this critique, the Commission proposes that the precautionary principle should be included among Sweden’s guiding principles for crisis management. However, as the debate on this principle during the last 30 years indicates, the principle is loaded with problems. I discuss one of these problems, namely its lack of clarity. I argue, however, that this problem is not unsurmountable. A principle is lacking clarity precisely by being a principle and not a rule with a well-defined meaning. As a principle it indicates a direction but does not prescribe a specific action. However, to be action-guiding its content needs to be specified by rational deliberation. With this in mind, I propose a framework for specification of the precautionary principle as applied to pandemics. The framework focuses on the principle’s four key elements: threat, uncertainty, action and responsibility. I also suggest certain general ethical restrictions on specification.