These findings may have major implications for managing patients already known to be at risk of severe COVID-19.
Why most people who get COVID have mild symptoms or none at all while some become severely ill is still a mystery – a mystery that scientists are urgently trying to solve.
Being obese or having existing health problems, such as diabetes or high blood pressure, are known to increase the risk of severe COVID. But this is not the whole story. Some seemingly healthy people can suffer from severe disease, too.
Early in 2020, scientists discovered that people with severe COVID had unusual levels of certain immune cells in their blood.
They included cells that are “first responders”, such as natural killer cells, as well as cells that develop after infection and specifically target cells infected with coronavirus, such as T cells. Scientists also discovered that these patients have changes in some cytokines – proteins that orchestrate the immune response.
This immune system “dysregulation” can cause damage to the lungs as well as other organs, such as the heart, liver and brain.
In severe COVID, the checks and balances that usually control the immune system seem to be altered. But the damage to the body’s organs is not caused by the virus itself but by the immune system’s response to the virus. Finding out who is at risk of this runaway immune response, before symptoms kick in, is important.
A new study, which has yet to be published in a scientific journal, sheds some light on the matter. The researchers, from the University of Cambridge, found that very early changes in the immune response to the virus could be used to predict who will develop severe disease and who won’t.
The scientists took 605 blood samples from 207 people with COVID and 45 healthy controls and measured their immune responses over 90 days. At the end of the study, they compared the immune responses of people who experienced severe COVID with people who suffered from mild disease or were asymptomatic.
They found that early in the infection, the immune systems of people with severe COVID produced higher levels of inflammatory cytokines, such as TNF-alpha, compared to people with mild disease.