Just within the past week, pharmaceutical companies have announced encouraging news about two COVID-19 vaccines in the final development phase. As more vaccine developers announce similar reports in the coming weeks and months, it’s key to remember that vaccine safety is as important as effectiveness against the virus. Fortunately, scientists have learned lessons from the rare vaccine mistakes of the past. Today, safety considerations are built into the development process, from the very first experiments in the lab, all the way through ongoing surveillance after a vaccine is in use. In practice this means that today’s vaccines should be among the safest ever created.