Increased platelet-neutrophil aggregate ratio after severe acute respiratory syndrome coronavirus 2 vaccination and severe infection.

ObjectivesPlatelet-neutrophil aggregates (PNA) bridge inflammatory processes with the hemostatic system. The goal of this study was the comparative evaluation of PNAs in healthy individuals vaccinated against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), septic patients, coronavirus disease 2019 (COVID-19) patients, and a pre-pandemic control group from 2019.MethodsThis observational study involved prospective blood sample collection from vaccinated individuals at separate times after immunization with Pfizer-BioNTech mRNA vaccine, together with the retrospective analysis of laboratory data from COVID-19, sepsis, and control subjects. PNA ratios and anti-S-protein antibody levels were also measured.ResultsFollowing primary SARS-CoV-2 vaccination, PNA levels increased significantly, showing a gradual decline over six months while remaining elevated. Booster vaccinations did not elevate PNA levels. In COVID-19 patients PNA ratios were the highest, while in the patients with sepsis remained comparable to those of the control group. A moderate correlation was found between PNA and anti-S-protein levels after primary immunization (rho = 0.31,  = 0.0071), but no correlation was observed post-booster. Strong associations between PNA and platelet counts occurred in COVID-19 and sepsis groups, while leukocyte and neutrophil counts showed no significant correlations with PNA.ConclusionsThe results of this study may support the possibility of using PNA ratio assessment for the evaluation of the immune response.