Older Australians are being urged to get the pneumonia vaccine, in a bid to boost immunisation numbers for the deadly infection.
Pneumonia is one of the top 10 killers in Australia, with 10 per cent of people hospitalised with the lung infection dying.
Professor Robert Booy is working to raise awareness of pneumonia, with less than half of those able to be immunised protecting themselves from the disease.
"If it's not deadly it can make you go from a relatively healthy older person to someone who is more dependent," he told AAP.
"You lose some independence, you go up the frailty scale even if you survive.
"It's not a friend to the old woman or the old man. It's not a friend at all."
Prof Booy says pneumonia and the flu can "hunt together", as most people carry the bacteria that causes pneumococcal pneumonia in their throat.
"The flu could damage the lining of the throat and allow the quietly sitting dragon to wake up and start destroying."
People over the age of 65 and at high risk of infection can get free pneumococcal vaccines from their GPs. Indigenous Australians are encouraged to get the vaccine from the age of 50.
Just one vaccine is needed but people with risk factors, such as those with impaired immunity or chronic illnesses, can get another shot after five years.
When Glenys Rentoul started getting cold-like symptoms she had no idea it was pneumonia, which kept her home from work for about five weeks.
The 66-year-old from Sydney has since recovered from the "awful" disease and is now encouraging at-risk adults to vaccinate against pneumococcal pneumonia.
"It's so debilitating if you survive it, if you're sick it's going to be quite a battle," Ms Rentoul told AAP.
She was hospitalised for about two days after she started coughing up spots of blood.
Ms Rentoul was overseas in New Zealand when she initially became sick, with her coughing and cold-type symptoms not improving despite a round of antibiotics after returning home.
"I wasn't expecting to get pneumonia at all, I just thought I had a bug and I'd get rid of it," she said.
"It was pretty full on and it wasn't pleasant, let's put it that way."
The 66-year-old spent several weeks feeling exhausted and had about five weeks off work before she began feeling like herself again.
