Do some people have hidden immunity against Covid?

Remember ‘immunity passports’? Back in April they were floated as a possible means by which we could all get back to a normal life. We could be tested for antibodies to SARS-CoV-2 – the virus which causes Covid-19 – and, if we tested positive, we could be allowed to go about our business. The presumption was that we would be immune from further infection, at least for a while. The idea quickly bit the dust. There was one good argument against it: it might encourage young people, who are very unlikely to come to harm from Covid-19, deliberately to set out to catch it in order to gain a positive antibody test and therefore an immunity passport.

Yet the government’s current position – that having Covid-19 cannot be trusted to give you any immunity against Covid-19 for any length of time (reiterated by the Prime Minister while explaining why he would have to self-isolate for a fortnight in spite of his body ‘bursting with antibodies’) – has always seemed bizarre.