Cytokine fingerprint differences following infection and vaccination - what can we learn from COVID-19?

COVID-19 vaccination and acute infection result in cellular and humoral immune responses with various degrees of protection. While most studies have addressed the difference in humoral response between vaccination and acute infection, studies on the cellular response are scarce. We aimed to evaluate differences in immune response among vaccinated patients versus those who had recovered from COVID-19. This was a prospective study in a tertiary medical centre. The vaccinated group included health care workers, who had received a second dose of the BNT162b2 vaccine 30 days ago. The recovered group included adults who had recovered from severe COVID-19 infection (<94% saturation in room air) after 3-6 weeks. Serum anti-spike IgG and cytokine levels were taken at entry to the study. Multivariate linear regression models were applied to assess differences in cytokines, controlling for age, sex, BMI, and smoking status. In total, 39 participants were included in each group. The mean age was 53 ±14 years, and 53% of participants were males. Baseline characteristics were similar between the groups. Based on multivariate analysis, serum levels of IL-6 (β=-0.4, p<0.01), TNFα (β=-0.3, p=0.03), IL-8 (β=-0.3, p=0.01), VCAM-1 (β=-0.2, p<0.144), and MMP-7 (β=-0.6, p<0.01) were lower in the vaccinated group compared to the recovered group. Conversely, serum anti-spike IgG levels were lower among the recovered group (124 vs. 208 pg/mL, p<0.001). No correlation was identified between antibody level and any of the cytokines mentioned above. Recovered COVID-19 patients had higher cytokine levels but lower antibody levels compared to vaccinated participants. Given the differences, these cytokines might be of value for future research in this field.