The present article examines – with some time lag – statements made by various Churches during the first phase of the Covid-19 pandemic. Especially in the Orthodox Church the ancient Eucharistic theological topos of the “medicine of immortality” is often used and applied to the pandemic context. However, this seems highly problematic in the light of modern medical knowledge and raises theological questions as well. Therefore, the original context of this topos as well as the Catholic doctrine of transubstantiation are taken into consideration. Finally, the article argues that Eucharistic theological reflection must always reflect anew philosophical and, in this case especially, scientific-medical challenges in order not to lose sight of the essence of the Eucharistic mystery. The pandemic could thus possibly lead to a renewed ecumenical reflection of Eucharistic theology.