https://www.scientificamerican.com/article/an-immune-protein-could-prevent-severe-covid-19-if-it-is-given-at-the-right-time1/

When the immune system fights viruses, timing is key. And this maxim may be especially true for its defense against the deadly severe form of COVID-19.

Several new studies of immune response to SARS-CoV-2, the virus that causes the disease, suggest timing could be critical for a class of proteins known as interferons, which are being researched as potential treatments. These immune proteins suppress viral replication early in disease. Yet if they are active later, some scientists think they can exacerbate the harmful inflammation that forces some COVID-19 patients onto life support. Interferons are “a double-edged sword,” says immunologist Eui-Cheol Shin of the Korea Advanced Institute of Science and Technology.