According to a new study, using electronic cigarettes may affect body's defences against pneumonia and flu.

The study claims that vapour produced by the devices affects the immune system in the lungs and leaves the human body vulnerable to infection bybacteria and viruses. This increases risk of pneumonia and fluin human body.

The team of scientists from John Hopkins University in Maryland exposed mice to e-cigarette vapour twice a day for two weeks at a level that is proportionally equal to the amount that a person, who uses e-cigarettes, will inhale. The team administered some of the mice with an influenza virus and others with the streptococcus pneumoniae bacteria that causespneumonia, sinusitis and other illnesses.

The team found that the group of mice that were exposed to the vapour were less able to fight illness and some died. Professor ShyamBiswal, senior author of the study, said the findings suggested "e-cigarettes are not neutral in terms of the effects on the lungs". The team said that that more tests must be conducted on humans to determine its effects.

Backers of the electronic cigarettes have said that they are useful in helping people quit the nasty habit. However, health officials say there is no concrete evidence to prove that and warned that such devices also known as vape pens and e-hookahs may lead people into the habit of smoking.