Australian researchers believe a decay in specific immune cells found in the lung could partly explain why older people struggle to overcome viruses.

Older people's struggle to fight off respiratory infections could be linked to the decay of specific immune cells in the lungs, a new Australian study has found.

Researchers from the Doherty Institute and Monash University have examined how lung tissue from organ donors of various ages responded to being infected with either influenza or SARS-CoV-2, the virus that causes COVID-19.

The study, published in Clinical & Translational Immunology, found that adult tissue responded in a way that was known to be able to limit the replication of the virus.

University of Melbourne and Doherty Institute researcher Linda Wakim says this was not the case for older donors.

"Interestingly, infection in the lungs of elderly donors did not result in this same rapid and robust antiviral response," Dr Wakim said on Tuesday.

"We were able to link this lag in antiviral response in the elderly to an age-associated decay of a specific immune cell in the lung, termed CD8+ tissue resident memory T cells, an immune cell designed to kill virus-infected cells."

Researchers believe this decay may at least partly explain why older people tend to struggle to shake off viruses.

Better understanding of age-associated changes in the lung immune response would help researchers develop strategies to boost or preserve such cells, Dr Wakim said.

"This will enhance local antiviral immune responses, and in turn improve the capacity of the elderly to combat respiratory infections," she said.

Neither adult nor elderly tissue was able to produce a rapid antiviral reaction after being infected with SARS-CoV-2.

Researchers said this was consistent with other studies which had described the new virus as not initially triggering a robust antiviral response.