A new study says there is not enough current evidence to show that e-cigarettes are an effective aid to help people stop smoking.
The Health Information and Quality Authority has published the first analysis comparing the cost-effectiveness of various smoking cessation interventions.
The cost to the healthcare system of smoking is about €460m a year.
There are around 820,000 smokers in Ireland, with half making at least one quit attempt each year.
Almost one in three people use e-cigarettes to try to stop smoking.
HIQA’s study says that while early evidence for e-cigarettes is promising, the Minister for Health should await the results of ongoing trials before recommending them as a smoking cessation method.
The health watchdog says that the most effective intervention is the prescription-only drug Varenicline, either alone, or alongside nicotine replacement therapy.
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Furthermore, it recommends that the HSE increase the uptake of the drug.
Speaking on RTÉ's News at One, HIQA's Director of Health Technology Assessment said it appears that e-cigarettes are "substantially safer" than tobacco cigarettes, in terms of smoking and passive smoking, but she said long term safety data is still awaited.
Dr Máirín Ryan said a new study in the UK showed there are "substantially less" toxins in the blood from e-cigarettes compared to tobacco cigarettes.
However, Dr Ryan said: "There's insufficient evidence at the moment to reliably demonstrate their effectiveness" in terms of cost and clinical effectiveness, and HIAQ will await the results of ongoing trials before deciding to recommend them".
She said there are six trials under way, involving up to 1,000 patients, that will provide results over the coming years.
Dr Ryan said there is also a concern that "increased uptake of e-cigarettes could lead to a re-normalisation and lead to increased uptake of people who've never smoked and ongoing migration to tobacco cigarettes from e-cigarettes".
Dr Ryan said there is some evidence in the US that teenagers are starting vaping rather than smoking and there is a concern that if they begin to vape, that they can become addicted to nicotine via that route.
She said there is also some evidence that some people have been migrating to tobacco cigarettes, and this would have to be taken into consideration if the HSE was to advocate that e-cigarettes should be recommended.