A new study (preprint, that is, not yet reviewed by independent experts or published in a journal) offers a ray of hope in the fight against coronavirus: almost all people who have been through the disease, regardless of their age, sex or severity of the disease, produce antibodies against the virus .
The study also suggests that anyone who has recovered from an infection can safely return to work, although it is unclear how long their protection would last .
Immunity
Most antibody tests are full of false positives – they detect antibody signals where there are none. But the new study was based on a test developed by Florian Krammer , a virologist at the Icahn School of Medicine at Mount Sinai, which has a less than 1 percent chance of producing false-positive results.
The new study is also by far the largest, with results from 1,343 people in and around New York City.
The study also alleviated the disturbing concern that only some people – only those who were seriously ill, for example – could produce antibodies. In fact, the level of antibodies did not differ according to age or gender, and even people with only mild symptoms produced a significant amount .
It should be noted that having antibodies is not the same as having immunity to the virus, but previous research has shown that antibody levels are closely related to the ability to neutralize the virus , the key to immunity.
Another finding from the study, that PCR diagnostic tests can be positive up to 28 days after the onset of infection, is also important. These tests look for genetic fragments, not antibodies, and suggest an active or waning infection. Researchers in South Korea recently announced , for example, that several suspected ‘reinfection’ cases were the result of PCR tests that collected dead virus remains .