On 5 May 2023, the World Health Organization declared that COVID-19 no longer constituted a public health emergency of international concern. Medical science must now consider how it ought to recalibrate its imagination and idealism in a post-COVID-19 pandemic world. The fact that advanced age was the largest risk factor for COVID-19 mortality and serious illness, as well as for the most prevalent chronic diseases, reveals the urgency and significance of shifting the focus from mitigating each specific pathology risk, one at a time, to targeting biological ageing itself. In his 1910 JAMA Address entitled 'Imagination and Idealism in the Medical Sciences', Christian Herter made an important distinction between two ways imagination and idealism can be invoked in the medical sciences: (i) humanitarian medicine, which emphasizes the obvious and direct paths of ameliorating human suffering; and (ii) a curiosity-oriented approach which explores pure science and the experimental laboratory. The latter examines the indirect ways of winning, in Herter's words, 'the citadel' of health promotion. Herter's reflections on these two contrasting approaches to medicine have significance for both the COVID-19 pandemic and the aspiration to promote the ideal of healthy ageing in the post-COVID-19 pandemic era.