Young Blood Vessels May Protect Children From Severe Coronavirus

Children may be protected from severe coronavirus complications because of their healthy blood vessels, a paediatric haematologist has said. Paul Monagle, from the Royal Children's Hospital in Melbourne, Australia, is planning a series of experiments to find out what happens when the virus enters the blood vessels and whether their younger, healthier vessels offer children some protection.

COVID-19 has been found to disproportionately affect older people, while children appear far less affected. Research from countries across the world shows the same pattern, with young people less likely to develop severe symptoms and require hospitalization. Why this is, is unknown. One suggestion is that their immature immune systems help as it stops an overreaction known as a cytokine storm from taking place. This is where the body's immune system goes into overdrive, which can lead to inflammation resulting in organ failure and death.

A feature that has emerged among severe COVID-19 cases is the development of blood clots. Research from Europe suggests that between 20 and 30 percent of critically ill patients will develop clots. Experts have also reported that patients develop "sticky" blood that is thicker than normal. Beverley Hunt, from King's College London, U.K., told the BBC that this sticky blood is contributing to mortality rates.

A correspondence by Swiss researchers published in The Lancet in April found the blood clotting seen in coronavirus patients may relate to a person's endothelium, Nature magazine reports. This is the layer of cells that coat the surface of blood vessels, providing a barrier between blood and body tissue. Clots normally form when tissue is damaged, with endothelium regulating this process. However, clots can also form if the endothelium is damaged.

Frank Ruschitzka, from the University Hospital Zurich, and colleagues looked at the endothelium of three COVID-19 patients who had died. They found the virus has entered these cells and caused inflammation with signs of clotting, Nature reports. The team said their findings suggest therapies to stabilize endothelium, while also tackling the virus, could help treat the disease.

Monagle told Newsweek that 71 percent of patients who die from coronavirus meet the clinical criteria for disseminated intravascular coagulation. This is a condition where small blood clots form through the bloodstream and block small blood vessels. Just 0.6 percent of people who recover from COVID-19 appear to have this condition. He said medicines that help prevent blood clots appear to help people with severe COVID-19 but how much and when these drugs should be administered is not clear.

He said a "likely explanation" for the differences of mortality rates between young and old appear to be the differences in the blood and clot structure. He believes children's developing endothelial blood interface protects them from becoming severely affected by COVID-19. To test this, he and his team plan to look at how the coronavirus affects clot formation in laboratory experiments using plasma and blood from children, adults and elderly people. "We will then test multiple potential drugs that could ameliorate the clotting effect, to determine the likely best candidates to take to a clinical trial," he said.

Monagle said they are starting to get results and plan to submit them for publication after looking at the quality and quantity. "I think it is possible this work will help with treatments and also may help to predict which patients are at highest risk," he said.

Stock image representing blood vessels. iStock