Politicians should not let history repeat itself by allowing e-cigarettes to be "pushed" at young people, Britain's chief medical officer has said.
Professor Chris Whitty added the long term effects of vaping could not be known for many years.
Last month, the Medicines and Healthcare products Regulatory Agency (MHRA) said it had received two reports of suspected e-cigarette or vaping associated lung injury (EVALI) in which the patients had died.
The regulator added that it had also received 20 reports describing 27 "serious respiratory events" linked to e-cigarettes, including pneumonia and lower respiratory tract infection.
Professor Whitty told the Daily Mail: "If you're just using them for a short period to come off cigarettes that isn't such a concern, but obviously if they're using them for long periods it can be, because we don't know what the effect will be and we won't know for many years."
He added that the Government should deal with any potential marketing of e-cigarettes towards children "very, very strongly".
NHS Digital's August figures showed that a quarter of pupils aged 11 to 15 reported they had used e-cigarettes in 2018 - the same as in 2016 - with regular e-cigarette use at 6%.
Professor Whitty said: "We need to make sure history does not repeat itself.
"The test of whether a product is being targeted at children is if it starts to be increasingly used by children and that will lead to action.
"If e-cigarettes are increasing in children then we should assume that they are being marketed towards them or at least pushed on them in some way, and deal with that very, very strongly."
