How fast can vaccination against covid-19 make a difference?

HOSPITALS AROUND the world are, once again, buckling under a torrent of covid-19 patients. In places as far apart as London, Cape Town and Los Angeles ambulances wait for hours to unload the sick, and refrigerated lorries have been brought in to hold the dead. Vaccines are the only way out of this. The question is, how quickly can they turn things around?Vaccines reduce deaths and hospital admissions in two ways: they protect the vaccinated directly, stopping them becoming ill; and they offer indirect protection to the unvaccinated, because those already jabbed will be less likely to infect them. Measuring the combined effect—and how quickly it kicks in—is possible only where mass vaccination is well under way. But early results are starting to arrive.