Coronavirus: low antibody levels raise questions about reinfection risk
- Scientists in Shanghai say some recovered patients show no signs of the neutralising proteins
- Early-stage findings could have implications for vaccine development and herd immunity, they say

A team from Fudan University analysed blood samples from 175 patients discharged from the Shanghai Public Health Clinical Centre and found that nearly a third had unexpectedly low levels of antibodies.
In some cases, antibodies could not be detected at all.
“Whether these patients were at high risk of rebound or reinfection should be explored in further studies,” the team wrote in preliminary research released on Monday on Medrxiv.org, an online platform for preprint papers.
Although the study was preliminary and not peer-reviewed, it was the world’s first systematic examination of antibody levels in patients who had recovered from Covid-19, the disease caused by the coronavirus, the researchers said.
All of the patients had recently recovered from mild symptoms of the disease and most of those with low antibody levels were young. The researchers excluded patients who had been admitted to intensive care units because many of them already had antibodies from donated blood plasma.