Researchers say COVID-19 antibody levels have fallen rapidly in the UK

The number of antibodies developed against COVID-19 decline ‘quite rapidly’ following infection, according to researchers from Imperial College London.

The REACT study, led by Imperial College London, analysed over 365,000 finger-prick tests carried out at home between 20 June and 28 September – these testing kits, known as Lateral Flow Tests, detect antibodies above a particular concentration in the blood.

From this analysis, the researchers found that the number of people testing positive for antibodies fell by 26.5% across the study period.

Between June and the beginning of July, around 60 people in every 1,000 had detectable antibodies for COVID-19. In September, however, this dropped to 44 people in every 1,000 testing positive for antibodies, the report found.

According to Imperial College London, this decrease was seen in all areas of the UK and across all age groups – although the trend was not observed in healthcare workers. The researchers added that this could indicate repeated or higher initial exposure to the virus.

In particular, the decline was most profound in people aged 75 and over compared to younger people and also in people with suspected rather than a confirmed infection.

Individuals living in London also had the highest number of positive antibody tests in the country – around twice the national average. In addition, health and care workers, ethnic minority groups and those living in deprived areas/large households had the ‘greatest burden’ of previous infection.

Overall, Imperial College London said that these findings suggest that there could be a decline in the level of immunity in the population over the months following the first wave of the coronavirus pandemic.

The researchers also added that it is still unclear to what extent antibodies offer immunity against the novel coronavirus, and for how long this protection lasts.

“This very large study has shown that the proportion of people with detectable antibodies is falling over time,” said Professor Helen Ward, one of the lead authors of the study report.

“We don’t yet know whether this will leave these people at risk of reinfection with the virus that causes COVID-19, but it is essential that everyone continues to follow guidance to reduce the risk to themselves and others,” she added.

Another separate arm of the REACT study is currently monitoring levels of current infection in the UK using at-home swab tests, involving over 150,000 people every month.

“If someone tests positive for antibodies, they still need to follow national guidelines including social distancing measures, getting a swab test if they have symptoms and wearing face coverings where required,” added Professor Paul Elliott, director of the programme at Imperial College London.