The study is based on a hypothesis with incomplete trials and hence the claim cannot be proven to be true.
The Guardian reported that the research team at Pitie-Salpetriere hospital in Paris questioned 480 patients who were tested positive for the virus and found that regular smokers are much less likely to develop a symptom or severe infection with COVID-19 compared with the general population.
The study has not been peer-reviewed and published. As it is a hypothetical study and needs more clinical trials, we consider the claim as unverifiable.
The COVID-19 pandemic has given rise to a lot of potentially dangerous misinformation. For reliable advice on COVID-19 including symptoms, prevention and available treatment, please refer to the World Health Organisation or your national healthcare authority.