Smoking habits predict adverse effects after mRNA COVID-19 vaccine: Empirical evidence from a pilot study

Objectives: The aim of this research was to investigate the possible association between smoking habits and the incidence of adverse effects (AEs) after mRNA COVID-19 vaccine. Study design: A longitudinal observational study was conducted on a sample of Italian healthcare workers. Methods: Healthcare workers who were administered the mRNA COVID-19 vaccine (either BNT162b2 or mRNA-1273) were evaluated for the occurrence of AEs after three vaccine doses. Multivariate Poisson regression analyses were fitted to predict AE risk according to smoking characteristics – such as number of tobacco cigarettes smoked per day, smoking time, and use of electronic cigarette (e-cig). Results: Of 320 total participants, 72 (22.5%) smoked cigarettes, and 50 (15.6%) used e-cig, 49 of which being dual users. Tobacco smoking significantly increased the risks of muscle and joint pain during the primary COVID-19 vaccination cycle and of chills during the whole vaccination series. The number of cigarettes smoked per day and vaping variously predicted AE onset during the whole cycle, with a tendency to respectively reduce and increase their risks. Duration of smoking did not affect any AE, except for headache after the booster dose. Most results remained significant after Bonferroni adjustment of significance level. Conclusion: Our pilot study indicated a possible effect of smoking habits on AE onset. Our research offers evidence that helps understanding possible predictors of the interindividual variability in COVID-19 vaccine response, serving as a reference for further studies on the effect of smoking on vaccine safety and effectiveness.