Down-regulation of SARS-CoV-2 neutralizing antibodies in vaccinated smokers

Vaccination is an effective approach to help control coronavirus disease 2019 (COVID-19). However, since the vaccines produce a heterogenous immune response, the risk of breakthrough infection is increased in vaccinated individuals who generate low levels of neutralizing antibodies (NAbs). It is therefore paramount in the fight against COVID-19 to identify individuals who have a higher risk of breakthrough infection despite being vaccinated. Here we addressed the effect of cigarette smoking on the production of neutralizing antibodies (NAbs) following COVID-19 vaccination since smoking profoundly suppresses the adaptive immune response to pathogen infection and the association between vaccination and smoking remains unclear. The SARS-CoV-2 Spike antibodies and NAbs (days 0, 14, 42, and 90) were measured in 164 participants received two vaccine doses of an inactivated vaccine (Sinovac-CoronaVac) longitudinally. Anti-Spike antibodies was elevated 14 and 42 days after COVID-19 vaccination compared to baseline (i.e., “Day 0”). Notably, RBD antibodies showed significantly higher expression in the nonsmoking group (n=153) than the smoking (n=11) group on day 42 (p<0.0001, Student’s t-test). NAbs continually increased after the first and second vaccine dose, peaking on day 42. NAbs titers then significantly decreased until day 90. Compared to nonsmokers, the NAb levels in smokers remained low throughout the period of testing. The median NAb titers in the smoking group was 1.40-, 1.32-, or 3.00-fold lower than that of nonsmoking group on day 14, 42, or 90, respectively. Altogether, our results indicate that smoking is a specific risk factor for COVID-19 breakthrough infection following vaccination.