THROUGHOUT the pandemic, SARS-CoV-2 has proved full of surprises, most of them nasty. Initially regarded as a respiratory virus, we now know it infects other organ systems, and can linger for months. It disproportionally kills people from poor and ethnic minority backgrounds and also men, for reasons that still aren鈥檛 fully understood. It doesn鈥檛 seem to be suppressed by warm weather or climates.
But the latest surprise is a nice one. Initial fears that the virus would fail to raise immune memory 鈥� the lengthy, sometimes lifelong, protection that we get from exposure to many viruses including measles 鈥� look exaggerated. It is still early days, but signs from patients point to a strong and long-lasting immune response (see 鈥�Can we become immune to the coronavirus? What the evidence says so far鈥�).
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That is welcome news for two reasons. It makes a vaccine more likely, and means that people who have recovered from the virus almost certainly can鈥檛 get it again, at least in the short term. But it also brings complications.
鈥淣atural herd immunity is for the birds. The levels of infection required would kill millions and devastate health services鈥�
One is that governments will be tempted to introduce 鈥渋mmunity passports鈥� for people who have recovered, perhaps permitting them to travel or attend large gatherings, which those without passports would be banned from. That may seem like a good idea, but bioethicists warn that it could backfire, for example by creating perverse incentives to get infected and a black market in stolen or forged passports. It could also be the start of a slippery slope to a more comprehensive system of health passports and surveillance.
The other fear is that it revives the canard that naturally acquired herd immunity will save us. That this was ever on the table beggars belief: without knowing whether natural immunity exists, positing herd immunity as an exit strategy is scientifically illiterate. Even now, natural herd immunity is for the birds. The levels of infection required would kill millions and devastate health services.
But herd immunity does remain the way out, if it is artificially created by vaccination. On that front, the latest science looks good. With infections rising globally (see 鈥�Lockdown measures return as covid-19 cases spike in several countries鈥�), we badly need it.
