Sinovac is an inactive vaccine produced against Coronavirus Disease 2019 (COVID-19) for almost a year. No sufficient information is available concerning provaccine immunogenicity. We investigated the efficacy of antibody response following vaccination of SARS-CoV-2-infected and noninfected healthcare workers by a two-dose inactive vaccine against COVID-19. The immunogenicity acquired on the 27th day and 42nd day after the first dose of vaccine (corresponding to Day 14 after the second dose) were compared by the demographics, immunosuppression, comorbidities, postvaccination reaction, and IgG levels of 120 subjects. The overall rate of second postvaccine seropositivity was 97.5% (n = 117) of all individuals, and 44 of these were seropositive after the first dose. The percentage of having a previous COVID-19 (59.1%) among seropositive individuals

Hepcidin is an important peptide hormone for iron homeostasis. It was shown to be increased in COVID-19 patients and may be a prognostic marker. In this study, the aim was to investigate serum hepcidin values and other iron metabolism parameters following the first and second COVID-19 vaccination. Thirty-eight healthcare workers were included in the study. Serum ferritin, hepcidin, iron, COVID-19 IgG and unsaturated iron binding capacity (UIBC) values were measured after the first vaccination (PRE) and second vaccination (POST). Changes and associations of serum parameters were statistically analyzed. It was determined that there was no statistically significant difference between the pre and post levels of ferritin (p=0.122), serum iron (p=0.127) or UIBC (p=0.145). Hepcidin was found to be significantly different between PRE and POST samples (p=0.0001). Hepcidin (PRE) was found to be significantly higher than the POST levels. Interestingly, there was no statistically significant relationship between the PRE and POST changes of ferritin and hepcidin (p=0.063). The association of PRE and POST changes of other parameters were also analyzed and a significant negative correlation between PRE and POST changes of serum iron and UIBC were found (rho=-0.751, p=0.0001). It was observed a decrease in hepcidin measures after second vaccination compared to the values after first vaccination. Vaccination affects serum hepcidin and this may be related with the interaction of hepcidin and the immune response.