Time-dependent changes of platelet and D-dimer parameters in vaccinated <i>versus</i> non-immunized COVID-19 patients

There are increasing data concerning changes in hematological (clinical) and biochemical blood tests in patients with COVID-19 infection, which indicate the severity of the manifestations of the infectious process. Coagulopathy often correlates with the severity of COVID-19 disease and the risk of death. In this regard, prediction of developing coagulopathy and its prevention remain quite relevant. The aim of our study was to identify differences in the content of platelets and D-dimer in patients with COVID-19. The study included cohorts of patients vaccinated against SARS-CoV-2, and those not immunized against this infection. A prospective, randomized, observational study of the patients response was performed in cohorts of 588/52.2% vaccinated (vaccinated) and 588/52.2% non-immunized (non-vaccinated) patients with diagnosed COVID-19 over the period from 23.06.2021 to 01.05.2022. The levels of blood platelets and D-dimer, as well as clinical outcomes of the disease in patients with COVID-19, were studied in dynamics on days 1-2, 5-6 and 10-12 of hospitalization. Upon admission, the normal value of the blood platelet counts did not differ between the compared groups, being 206.58 109 in vaccinated group and 204.85 109 in the unvaccinated group, respectively. a moderate increase in the concentration of D-dimer was noted in both groups upon admission, i.e., 2838.60 ng/mL in the group of vaccinated patients and 3242.08 ng/mL among the unvaccinated patients. In the course of the study, we have shown that the dynamics of D-dimer index in vaccinated versus non-immunized persons was similar according to the days of disease, showing an increase from the first day and a trend towards an higher values, starting from 5-6 days. At the same time, the dynamics in the vaccinated patients was somewhat less favorable than that of the non-immunized subjects. In the patients who were not immunized throughout the entire observation period, the platelet count exceeds the levels found in vaccinated subjects, thus suggesting higher risk of thrombosis and cytokine storm. The data obtained show that the dynamics of D-dimer and platelet counts in vaccinated and non-immunized people is similar on appropriate terms of the illness. However, the changes are more pronounced in vaccinated cohort, but it does not indicate a greater risk of adverse outcomes.