Ephemeral Immunity?

A study carried out by Imperial College London has tracked the levels of antibodies in the bloods of 365,000 randomly-selected adults since the first wave (March-April) of the pandemic in the UK (https://uk.reuters.com/article/health-coronavirus-britain-antibody/uk-study-finds-evidence-of-waning-antibody-immunity-to-covid-19-over-time-idUKL8N2HH5F1). The subjects were sent finger-prick tests to carry out on themselves at home. One cannot be too confident about all the results in such cases (there may be false positives and false negatives). They found that 6% of the population had antibodies at the end of June but this declined to 4.4%, after lockdown, in September. They interpreted this as suggesting that the protective blood antibody response (at least from an infection) can be relatively short-lived. There were some additional indications e.g. younger age groups and those with symptoms appeared to have longer-lasting antibody levels than older or asymptomatic counterparts. Healthcare workers also showed little evidence of a decline due, they suggested, to repeated exposure to the virus. The results seem to broadly chime with the experience seen in Manaus (Brazil), where there was little evidence of 'herd immunity', in a widely-infected, young population. Studies in Sweden (with no lockdown), have also suggested that blood antibodies are not very persistent. The very fact that there are increasing reports of reinfections, by this virus, also supports the view (along with the disappointing results for treatments with 'convalescent plasma'). Antibodies are, of course, not the whole story, as activated T and B cells may stilloffer some protection from the virus. It is also possible that some vaccines might be able to generate a longer-lasting response than an actual infection. One thing is, however, certain, namely that the immune respose to sars covid2 is complex and it is unlikely that there will be simple protections.