The race is on to develop a vaccine that can protect us from the COVID-19 pandemic. An impressive 115 vaccine candidates are currently being investigated, but it is still many months before a vaccine might be approved. Sarah L Caddy writes in The Conversation that we already have hundreds of licensed vaccines for over 25 different viruses and bacteria that infect humans. We can protect ourselves against infections ranging from cholera to rabies. The common aim of all vaccines is to induce an immune response that prevents future disease. Is it possible that one of these existing vaccines could also induce protection against SARS-CoV-2, the virus causing COVID-19? Repurposing drugs is a popular strategy for treating COVID-19, as exemplified by the many trials using the Ebola drug remdesivir, or the antimalarial drug hydroxychloroquine. If an already-approved vaccine could reduce the severity of COVID-19, this would be really good news. The BCG vaccine has received recent attention for being a widely used vaccine that may help control COVID-19. A handful of studies identified an interesting association between the severity of COVID-19 in a country and how many of the population were vaccinated with BCG. The BCG vaccine apparently reduces the damage caused by COVID-19.