Melbourne scientists uncover reason why COVID-19 hits the elderly hardest

Melbourne scientists may have uncovered the reason why COVID-19 hits the elderly hardest.

A history of overcoming less severe strains of coronavirus could be working against the elderly.

The elderly may be hit far harder by COVID-19 because their immune systems have developed a false sense of security to previous colds and coronaviruses, scientists believe.

New research from Melbourne’s Doherty Institute suggests a history of overcoming less severe strains of coronavirus has left older people around the globe unable to cope fully with the SAR-CoV-2 virus responsible for COVID-19.

The latest study also sheds light on why children, with little or no previous exposure to other coronaviruses, have coped far better throughout the pandemic.

However, the findings turn conventional understanding about the way humans respond to viruses on its head.

Typically a person’s immune system learns how to fight off a virus when it is first exposed to it, then remembers the antibodies required so they are protected if they ever come into contact with the same or a similar strain again.

But a team led by Dr Amy Chung, found the immune systems of elderly COVID-19 patients were not able to recognise SAR-CoV-2 as being different and more dangerous than previous coronaviruses that cause a common cold, so were tricked into rolling out the same ill-equipped defence.

“The elderly, because they have lived these really long amazing lives, have been repeatedly exposed to these coronavirus so they don’t actually get sick because they have seen that human coronavirus again., and again, and again,” Dr Chung said.

“But when they get exposed to COVID-19 for the first time, and because there are so many similarities in some parts of the coronaviruses, they probably see this new SAR-CoV-2 and think it is similar and therefore target parts of the virus that are more similar.

“Because they have been exposed to these human coronavirus again and again they have this expectation they should be targeting and inducing these types of immune responses, and therefore they don’t recognise that this is quite a different virus.”

Results of the Melbourne study published in Nature Communications show significant differences in the blood samples from 89 children, 98 adults, 57 elderly individuals and 50 COVID-19 patients.

Through a cutting-edge process called systems serology researchers Dr Kevin Selva, Dr Carolien van de Sandt and collaborators at the University of Michigan were able to identify the hundreds of antibodies each patients’ immune systems had generated over their lives – effectively revealing all viruses they have come into contact with and then overcome.

Dr Chung said those people who had previously fought off similar viruses including SARS-CoV-1, MERS-CoV, and viruses that cause the common cold, were not as capable as generating new types of antibodies specifically for COVID-19.

Children and those experiencing SAR-CoV-2 as a completely new invader were more likely

strong, targeted immune response against COVID-19, the researchers found.

As well as providing a better understanding of why older people were more at risk from COVID-19, Dr Chung said the revelations would help assess and improve more targeted vaccines.