Alongside access to clean water, vaccination prevents more child deaths than any other health intervention [Reference Shattock, Shattock, Johnson, Sim, Carter, Lambach, Hutubessy, Thompson, Badizadegan, Lambert, Ferrari, Jit, Fu, Silal, Hounsell, White, Mosser, Gaythorpe, Trotter, Lindstrand, O’Brien and Bar-Zeev1].