That suggests COVID-19 may in fact be five times more prevalent than suspected. It also means it may be five times less deadly than predicted.
The study,2 "Systemic and Mucosal Antibody Secretion Specific to SARS-CoV-2 During Mild Versus Severe COVID-19," was posted on the prepublication server bioRxiv, May 23, 2020. According to the authors:
"When symptomatic, COVID-19 can range from a mild flu-like illness in about 81% to a severe and critical disease in about 14% and 5% of affected patients, respectively."
The Swiss study,3 which sought to investigate SARS-CoV-2-specific antibody responses, found that even though people who had been exposed to infected individuals had SARS-CoV-2-specific immunoglobulin A (IgA) antibodies in their mucosa, there were no virus-specific antibodies in their blood.
IgA is an antibody that plays a crucial role in the immune function of your mucous membranes, while IgG is the most common antibody that protects against bacterial and viral infections and is found in blood and other bodily fluids. As explained by the authors:4
"As with other coronaviruses, symptomatic SARS-CoV-2 disease causes an acute infection with activation of the innate and adaptive immune systems. The former leads to the release of several pro-inflammatory cytokines, including interleukin-6 …