Is this the key to understanding Covid immunity?

Just how strong an immunity do Covid patients develop after they have acquired the infection and how long does it last? The question is vital to the likely future passage of the pandemic, and to how well vaccines will protect us in the long term. Several studies have suggested there is a sharp decline in antibodies to SARS-CoV-2 over time – a paper from Imperial College’s React study in October, for example, revealed that the proportion of the population showing antibodies to the virus declined from 6 per cent in June to 4.4 per cent in September. The researchers were at pains to emphasise that the presence of antibodies does not indicate immunity to Covid-19, but many people have taken it as an indication that immunity to the disease quickly declines after infection. Since then, a study of 12,500 healthcare workers in Oxford has suggested that naturally-gained immunity from having Covid-19 is, after six months, on a level similar to that of the Pfizer vaccine.