It is necessary to examine the use of e-cigs as a harm reduction tool in comparison to smoking cigarettes. Placing a foreign substance in the lungs will never be "safe" but in comparison to smoking the harm is greatly reduced according to this, ( https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/457102/Ecigarettes_an_evidence_update_A_report_commissioned_by_Public_Health_England_FINAL.pdf ) about 95% safer. In terms of pneumonia I would assume the same holds true in comparison.