Asymptomatic coronavirus patients appear to lose detectable antibodies sooner than people who have exhibited Covid-19 symptoms, according to one of the biggest studies of its kind in Britain published on Tuesday, news agency AFP has reported. The findings by Imperial College London and market research firm Ipsos Mori also suggest the loss of antibodies was slower in younger sufferers compared to the elderly. The research has also indicated that people's immune response to Covid-19 reduces over time following infection.