Scientists have warned people not to smoke after a French study has suggested smokers could be less likely to get symptomatic coronavirus.

Researchers in France have put forward the idea that nicotine could protect against infection, and one study has shown an unusually low proportion of Covid-19 patients in hospitals to be smokers.

Clinical trials are in the works, according to a Paris hospital trust.

However, public health experts have warned smoking remains a risk factor for the virus taking a more serious turn.

Professor John Britton, the director of the UK Centre for Tobacco & Alcohol Studies, told The Independent smokers who contract coronavirus are more likely to end up in intensive care than non-smokers with the virus.

“Nicotine could protect you and the trial is really interesting,” the professor of epidemiology at the University of Nottingham said. “But the message to smokers should be exactly the same, which is stop.”

Professor Linda Bauld from the University of Edinburgh said: “If people already have a smoking-related disease, we know they are going to get worse outcomes from Covid-19.”

She said people who smoke can also react less well to ventilators, and can take more time to recover after a stint in hospital.

“There has never been a better time to quit smoking in the face of a respiratory pathogen like Covid-19,” she said. “But nicotine might be an interesting medicine to investigate to see if it helps amongst other treatments.”

French researchers have suggested nicotine may help prevent and control a coronavirus infection, and said they plan on doing a trial using nicotine patches.

Data from a university hospital has found a smaller proportion of people in hospital with the virus are smokers compared to the general population.

Around 8 per cent of hospitalised patients said they smoked, compared to 25 per cent of the French public.

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These findings could be down to people laying off cigarettes due to suffering with coronavirus, which affects breathing and lung function, according to Dr Lion Shahab, an associate professor in health psychology at University College London.

“The low proportion of current smokers might be because people cannot actually smoke when they have the disease,” he told The Independent.

He said the “jury was still out” as to whether nicotine could protect people against the disease, but said smokers may still be more likely to catch the virus due to the habit of smoking, which involves bringing their hands very close to their face.

Following the hospital data, the head of France’s national health agency said there was no concrete evidence yet that nicotine helped stave off the disease, and warned smoking remained France’s number one killer.

France has been one of the worst-hit countries during the coronavirus pandemic, with more than 158,300 confirmed infections to date.

The nationwide lockdown — which has restricted people’s movements and banned all public gatherings since mid-March in a bid to tackle the outbreak — saved around 61,000 lives in its first month, a new study has claimed.

The death toll for Covid-19 patients stood at 21,340 on Thursday, according to a Reuters global count.