The Latest on Coronavirus and Immunity

There’s a possibility that immunity might not last

In recent weeks, antibody testing has dominated the Covid-19 conversation because of its exciting potential to identify who is immune to the disease. The basic idea is that people who test positive for Covid-19 antibodies must have already been infected, meaning that their immune systems can protect them from reinfection as they step out into the slowly reopening world.

If this sounds too good — and simple — to be true, that’s because it is: There are…