New research has found that coronavirus antibodies drop substantially over a short period following the initial wave of infection, casting yet more doubt over the possibility of herd immunity. A major study led by Imperial College London, involving 365,000 participants in England and conducted between 20 June and 28 September, showed the number of people testing positive for antibodies fell by over 25 percent across the study period – from almost roughly six percent to 4.4 percent. The downward trend was observed in all areas and across all age demographics, except for healthcare workers, which probably indicates higher initial exposure to the virus, or repeated exposure, among this group. The Real Time Assessment of Community Transmission (REACT) study involving home-administered finger-prick tests showed the decline was slower among 18-24 year-olds versus people aged 75 and above. Antibodies indicate when a person has previously been infected with the virus and are a useful marker to