 History reminds us, when the world is faced with an unsurmountable challenge, the greatest leaders stand together and act in the common interest of all. Together, we can achieve great things, not because they are easy, but because they are hard. COVID-19 is the greatest challenge of our time. A global crisis that the world has not seen in a generation. Science has provided the first tests, treatments and vaccines needed to save lives. But with a growing divide between the haves and have-nots, we risk leaving people behind. No one is safe until everyone is safe. The WHO Act Accelerator is the only global collaboration that conceals through this. But with a critical funding gap, we urgently call on world leaders to stand together and to share the burden of responsibility fairly, to fully fund the Act Accelerator, to immediately share surplus vaccines and ensure science keeps pace with the pandemic. This investment will save lives. It will prevent health systems collapsing. It will restore global economies. We must act decisively, not individually but collectively. Now is the time to pull the world back from the precipice of immeasurable suffering, to make decisions that will be remembered for a hundred years, as we remember the might and collective endeavour of our heroes, both past and present. The time to act is now. To act together, to save lives, to invest in the Act Accelerator.