A study found vapour from electronic cigarettes could be as bad as traditional tobacco or even vehicle exhaust at sticking harmful bacteria to the airways, increasing chances of the inflammatory lung condition.
Tests on both humans and mice by Queen Mary University of London found the effect was present in both nicotine and non-nicotine e-cigarettes.
The research examined the effects of vaping on a molecule produced by the cells that line the airways called PAFR (platelet-activating factor receptor), which previous research has shown helps stick bugs associated with pneumonia to the nose, throat and lungs.
The team studied the cells lining the nose of 17 regular e-cigarette users one hour after vaping, and found the PAFR levels had tripled compared to normal levels.
They suggested that people at high risk of pneumonia consider using nicotine patches or gum as alternative means of giving up traditional cigarettes.
Professor Jonathan Grigg, who led the research, said: “Together, these results suggest that vaping makes the airways more vulnerable to bacteria sticking to airway lining cells.
“If this occurs when a vaper gets exposed to the pneumococcal bacterium, this could increase the risk of infection.
“Some people may be vaping because they think it is totally safe, or in an attempt to quit smoking, but this study adds to growing evidence that inhaling vapour has the potential to cause adverse health effects.”
Pneumonia is the sixth biggest cause of death in the UK, killing 29,000 people a year with deaths mainly occurring in older people and children and babies under 10 years.
Around 220,000 people receive a diagnosis of pneumonia each year, including, last year, Jeremy Clarkson, a smoker, who said he nearly died from the condition.