Covid-19 vaccines flirted with perfection at first. Reality is more complicated
When Covid-19 vaccines were reported last fall to be roughly 95% effective at preventing symptomatic Covid-19 infections, the world rejoiced — and even veteran scientists were blown away. Very few vaccines are that protective. Those made to fend off viruses like SARS-CoV-2 — viruses that invade the nose and throat, like flu — typically aren’t at the high end of the efficacy scale.
That was the good news. Now, however, our soaring expectations for Covid-19 vaccines are in the process of sinking back to earth.
