Smokers are likely to be more vulnerable to COVID-19 as Coronavirus is an infectious disease that causes respiratory illness (like the flu) with symptoms such as a cough, fever, and in more severe cases, difficulty breathing.
The act of smoking means that fingers (and possibly contaminated cigarettes) are in contact with lips which increases the possibility of transmission of virus from hand to mouth.
Smokers may also already have lung disease or reduced lung capacity which would greatly increase risk of serious illness.
Smoking products such as water pipes often involve the sharing of mouth pieces and hoses, which could facilitate the transmission of COVID-19 in communal and social settings.
Conditions that increase oxygen needs or reduce the ability of the body to use it properly will put patients at higher risk of serious lung conditions such as pneumonia.