France has banned online sales of nicotine substitutes, and limited sales in pharmacies.

The idea is to prevent a run on nicotine replacements, after a widely reported study from a Paris hospital found smokers were less likely to be admitted to hospital with COVID-19.

The theory is that nicotine, which attaches to cell receptors, blocks the virus from entering those cells.

French researchers plan to test nicotine patches on patients and health workers.

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France on Friday banned online sales of nicotine replacements — such as nicotine gum and patches — after a widely reported Paris study found smokers were less likely to admitted to hospital for COVID-19.

In a draft legal text published earlier this week, the government warned there could be a run on nicotine replacements thanks to the study. Pharmacies dispensing treatments for tobacco addiction must limit the amount they issue to an individual patient to a single month's supply.

The text states: "Because of media coverage around the possible protective action of nicotine against Covid-19, there is a strong risk that the dispensing in pharmacies and internet sales of nicotine replacements will experience a surge in the coming days."

The government said the ban would stop people from rushing out and potentially over-consuming nicotine substitutes, as well as ensure a steady supply for patients genuinely being treated for smoking addiction.

The decree comes after a Paris hospital study found that the infection rate for smokers among COVID-19 patients was lower than non-smokers. The study factored in around 480 patients at the Pitié-Salpêtrière hospital. French researchers now plan to hand out nicotine patches to COVID-19 patients and frontline health workers to explore the theory further.

According to Jean-Pierre Changeux from France's Pasteur Institut, a co-author of the study, the theory is that nicotine may adhere to cell receptors, thus blocking the virus from entering people's cells.

Still, the researchers warned of the dangers of nicotine in their study, and that smoking remains extremely dangerous for your health.

And overall, the research on smoking and nicotine's impacts on COVID-19 patients is nascent. Scientific American notes there's a considerable body of research to show that smoking reduces lung function and increases flu risk. And a study in the New England Journal of Medicine suggested Chinese smokers who contracted COVID-19 were more likely to get severe infections. An overview of the current studies on the link between COVID-19 and smoking suggested that COVID-19 patients who smoked were more likely to be admitted to intensive care.