Summary
Introduction. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused a pandemic of coronavirus disease 2019 (COVID-19). This pandemic affected the whole world; with 1.25 million cases and 9 thousand deaths in Lithuania to date. Healthcare workers (HCW) are at increased risk for COVID-19 infection, due to the frontline nature of their work. COVID-19 messenger ribonucleic acid (mRNA) vaccine encodes full-length code of the spike (S) protein. These vaccines have been shown to offer protection by stimulating production of immunoglobulin (Ig) G. IgG antibodies against receptor binding domain (RBD) with neutralization activity are capable of inhibiting SARS-CoV-2 binding to the angiotensin-converting enzyme 2 (ACE2) receptor. Quantitative detection of IgG antibodies were detected by the chemiluminescent microparticle immunoassay (CMIA). The purpose of the study was to evaluate the immune response to COVID-19 mRNA vaccine in healthcare workers based on the data from specific antibody tests post-vaccination.
Materials and methods. In this study, a total of 9955 serum samples from five groups: HCW before vaccination (n=2438), HCW 3 months after the 2nd vaccine dose (n=2542), HCW 6 months after the 2nd vaccine dose (n=2619), HCW 3–4 months after the 3rd vaccine dose (n=916) and HCW 5–6 months after the 3rd vaccine dose (n=1440) were analysed. Antibody induced immune response was evaluated according to the World Health Organization (WHO) guidelines.
Results. The highest concentration mean (1927.2±83.9 BAU/ml) and median (1309.6 BAU/ml IQR 732.1–2553.3) of antibodies was among the HCW 3–4 months after 3rd vaccine dose group; also the majority of HCW in this group (76.2 %) had a strong (≥700 BAU/ml) immune response. After the 2nd dose of the vaccine, the women group had stronger immune response, whereas after the 3rd vaccine dose, the immune response in women and men did not differ significantly. After 2nd vaccine dose the youngest HCW had stronger immune response than older HCW. However, after the 3rd vaccine dose, majority of all the HCW had strong immune response regardless of age. After the 2nd vaccine dose, the younger men and younger women had stronger immune response, however after the 3rd vaccine dose, older women had the strongest immune response; meanwhile, the older men had the weakest immune response.
