COVID-19 Pandemic
Smoking and time to SARS-CoV-2 Reinfection: an analysis of reinfection-free time in a prospective cohort study Keith Gray* Keith Gray Gray Gray Gray Gray Gray Gray Gray Boston University School of Public Health
Background:
Smoking is associated with immune system dysregulation and increased severity of acute COVID-19. However, the effect of smoking on susceptibility to repeat SARS-CoV-2 infection in the Omicron era is poorly understood. Understanding whether smoking influences reinfection risk in real-world conditions is important as COVID-19 is now endemic and reinfections are common.
Methods:
We used data from the VISION study, a prospective cohort of adults in North Carolina with acute COVID-19 to estimate the effect of baseline smoking history (ever vs never) on time to SARS-CoV-2 reinfection. The primary estimand was the difference in restricted mean survival time through 365 and 448 days, the maximum follow-up. Secondary analyses were conditioned on vaccination to assess robustness. We also fit a marginal structural Cox model over 448 days using inverse probability weights to adjust for baseline confounding, time-varying vaccination, and study dropout with robust variance estimation.
Results:
Among 3,190 participants analyzed (829 ever smoked), 583 reported a reinfection over a median of 448 days (interquartile range: 255, 448) follow-up. Ever smokers experienced 8.4 fewer reinfection-free days through 365 days (95% CI: −15.6 to −1.2) and 11.9 (-21.6, -2.2) fewer days through 448 days compared to never smokers in crude analyses. Conditioning on ever receiving a vaccine over at-risk follow-up, these differences increased to 9.7 (95% CI: -16.8, -2.7) and 13.7 (-23.2, -4.2) fewer days through 365 and 448 days, respectively. In our marginal structural model, ever smoking was associated with a higher hazard of reinfection (HR: 1.25, 95% CI: 1.00 to 1.57).
Conclusion:
Smoking was associated with shorter reinfection-free time and increased risk of SARS-CoV-2 reinfection. The widening difference with longer follow-up suggests a cumulative disadvantage for ever smokers. These findings emphasize the importance of SARS-CoV-2 prevention for people who have ever smoked.