Association between COVID-19 severity and tobacco smoking status: a retrospective cohort study using propensity score matching weights analysis oleh Musaad A Alshammari, Ahmad Alamer, Lina Al Lehaibi, Mashael Alghamdi, Haneen Alotaibi, Mukhtar Alomar, Fawaz Alasmari, Faleh Alqahtani, Abdualziz Alhossan, Tahani K Alshammari