Bacterial ligands in the rehabilitation of healthcare workers after COVID-19

Immune defense mechanisms in survivors of the COronaVIrus Disease-19 (COVID-19) and development of their rehabilitation during the pandemic both portray a great scientific and practical interest.The aim of the study was to explore effect of Immunovac-VP-4® (I-VP-4), a vaccine based on bacterial ligands, on the clinical and airway mucosal immunity parameters, along with systemic immune response in a group of medical workers in post-COVID period and in persons who did not develop the disease.Methods. 82 healthcare workers aged from 18 to 65 years were included in a prospective open controlled study. The participants were divided into 4 groups: groups 1 (n = 20) and 2 (n = 27) included those with a history of COVID-19, and groups 3 (n = 18) and 4 (n = 17) included those who did not have the disease. Volunteers in groups 1 and 3 received I-VP-4. Samples of oral fluid, induced sputum, nasopharyngeal and oropharyngeal mucosa scrapings, and venous blood were examined. The levels of total secretory immunoglobulin class A (sIgA) and immunoglobulin G (IgG) were determined by enzyme immunoassay. The phagocytic index (PI) of leukocytes was assessed by flow cytometry.Results. The group of patients who did not have COVID-19 and received IVP-4 (Group 3) showed a tendency to a smaller number of COVID-19 cases, as well as some reduction in days of incapacity for work due to the acute respiratory infections (ARI). The vaccine improved airway mucosal immunity parameters and innate immune response. sIgA increased in the induced sputum (p < 0.005) and unchanged in the oropharyngeal mucosa samples in Group 1. The PI of macrophages in oral fluid doubled (p < 0.05) in this group. At the same time, those parameters decreased in Group 2. In non-infected vaccinated patients (Group 3), a significant increase of PI of blood monocytes was found on the day 90 of the study (p < 0.05). Also, a four-fold increase of PI of macrophages in oral fluid in comparison with Group 4 (p < 0.05) was noted.Conclusion. I-VP-4 improved airway mucosal immunity mechanisms and the systemic immune response. The vaccine can be recommended for rehabilitation programs for COVID-19 survivors and for prevention of ARIs.