As United States reveals its plan to offer an extra dose of COVID-19 vaccine, equity and scientific questions abound.
A version of this story appeared in Science, Vol 373, Issue 6558.
As the extraordinarily infectious Delta variant of SARS-CoV-2 continues to spread around the world, vaccines’ powers are showing their limits. Although they are still extremely effective at preventing severe COVID-19, the tantalizing hope that the shots could block almost all infections—and squelch transmission—has evaporated. That has upended return to office and school plans, threatened economic recoveries, and spurred fresh political rows over mask and vaccination mandates.