In 1956 The Netherlands experienced a major outbreak of poliomyelitis with over 2200 patients. A vaccine was in reach, and it was used. Now, polio is nearly eradicated globally with vaccinations. In 2020 a similar situation occurred with COVID-19. Large-scale vaccinations form an essential tool to combat the epidemic. This article describes uncertainties to start both mass vaccination campaigns, and reflects on similarities and differences then and now.