Since COVID-19 emerged in December 2019, it has drained resources in yellow fever hotspots, and delayed lifesaving vaccination campaigns, increasing the risk of outbreaks. Despite this, 48 million people were still vaccinated against yellow fever in 2020. How does this happen in the midst of a pandemic? And what can that pandemic teach us about combatting yellow fever in the future? We get the perspectives of Dr Mike Ryan, who heads up WHO's response, and Dr Chikwe Ihekweazu, Head of the Nigeria CDC.