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MOST people still don’t have any level of immunity to the virus behind covid-19. But there is a growing risk that some of us are becoming immune to the enormous numbers that this pandemic is throwing out on a weekly basis.

As New Scientist went to press, the world was on track to exceed a million deaths from covid-19 within days (see “Coronavirus death toll nears 1 million – how did we get here?”). That is a number that we shouldn’t allow ourselves to become blasé about.

Early in the pandemic, US President Donald Trump suggested covid-19 wasn’t as …