The goal of "herd immunity" is often described as just around the corner, signalling a return to pre-pandemic normality.
But will we actually get there?
Probably not, say epidemiologists and mathematicians who have been studying the latest numbers closely. At least, not any time soon.
These experts highlight several major barriers that stand in the way: the arrival of new COVID-19 variants, vaccine hesitancy among adults and the fact that millions of children can't be vaccinated at all. Even in a best-case scenario, this makes the herd-immunity threshold a high bar. Practically speaking, it could be out of reach.