question: In early 2021, cases of rare adverse events were observed in individuals who had received the Astra Zeneca COVID-19 vaccine. Countries around the world differed radically in their policy responses to these observations. In this paper, we outline the ethical justification for different policy approaches for managing the emerging risks of novel vaccines in a pandemic. We begin by detailing the precautionary approach that some countries adopted, and distinguishing ethical questions regarding the management of known and unknown risks. We go on to outline the harms of adopting a highly precautionary approach in a pandemic context, and explain why an appropriate policy approach should accommodate the benefits as well as the risks of vaccination. In the final section, we outline three policy approaches that can accommodate the different benefits of vaccination, whilst taking into account the harms of precaution. Whilst we do not set out to defend one particular policy approach, we explain how different moral theories lend different degrees of support to each of these different approaches. Our analysis elucidates how fundamental value conflicts in public health ethics played out on the global stage of vaccine policy.