Could ‘antigenic drift’ and ‘antigenic sin’ set back the fight against Covid?

Of the many things that might still go wrong with Covid, the government scientific advisory group Sage has warned, is a possible combination of “antigenic drift” and “antigenic sin”. This does not describe a louche jet-setter, but something rather more alarming.

An “antigen” (first recorded in English in 1908) is any foreign substance that, when introduced to the body, stimulates the production of an antibody. Etymologically, it creates (“-gen”) an “anti”. An antigen can be a pathogen (from the Greek “generates suffering”), such as the Sars-CoV-2 virus, or a vaccine. So what is antigenic is good for you, as Nietzsche might have said, unless it kills you first.

But what of drifting and sin? “Antigenic drift” is random genetic variation, which will probably result in a virus strain against which current vaccines are ineffective. And “antigenic sin” is the human body’s regrettable tendency to fall back on its immune memory of previous antigens when presented with a new variant of either virus or vaccine. This phenomenon was first named, jokily, as “antigenic original sin” in 1960, though its heathen humour might be lost on those who prefer to locate the real antigenic sinners in the corridors of government.

Steven Poole’s A Word for Every Day of the Year is published by Quercus.

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