Genetically predetermined limit on the immune system may be the key to why Covid has such a devastating effect on the elderly, according to a modelling study.

Researchers at the University of Washington (UW) in the US noted that the immune system’s ability to combat Covid, like any infection, largely depends on the replication of the immune cells effective at destroying the SARS-CoV-2 virus that causes the disease.

The study, published recently in The Lancet eBioMedicine journal, suggests that the body’s ability to produce these cloned immune cells, which cannot be infinitely created, falls off significantly in old age.

”When DNA split in cell division, the end cap — called a telomere — gets a little shorter with each division,” said professor James Anderson, a modeller of biological systems at UW.

”After a series of replications of a cell, it gets too short and stops further division. Not all cells or all animals have this limit, but immune cells in humans have this cell life,” Anderson said in a statement.