Vaccines save lives, but far too many children in the world are not being vaccinated. The COVID-19 pandemic only added to their numbers. The children who are missing out live in the poorest, most remote and most marginalized communities. To reach them, it is vital to prioritize investment in primary health care and in the health workers – mostly women – who deliver services. It is essential, too, to build confidence in vaccines and to make the most of a host of new ideas and technologies that can boost the power of vaccines and ensure they reach every child.