Antibodies few and short-lived, lung abnormalities found in asymptomatic carriers.
A new study on COVID-19 immunity has found that people who were asymptomatic or mildly symptomatic had their antibodies diminish within two to three months. Though larger studies are needed, the findings cast doubt on antibody testing and herd immunity.
A closer look at people who tested positive for COVID-19 but never developed symptoms has found that such asymptomatic carriers have few to no detectable antibodies just weeks after infection, suggesting they may not develop lasting immunity.
There's growing evidence that a significant proportion of people who test positive for COVID-19 never show symptoms, although it's not clear what percentage of people that is and what role they play in spreading the disease.
A Chinese study published this week in Nature followed 37 people in Wanzhou District in China who did not show any outward signs of the disease, despite testing positive when their respiratory tracts were swabbed and being kept in hospital for observation.
The study also found that despite having no outward symptoms, 70 per cent had lung abnormalities detectable in X-rays at some point during infection — mostly spots called "ground-glass opacities," which can indicate inflammation or other signs of disease.
What was "a little bit surprising," he said, was the fact that 40 per cent of people with asymptomatic infections had no detectable antibodies at all.