A study published in the British Journal of Hematology describes that coronavirus disease 2019 (COVID-19) vaccines are effective in reducing thrombotic events and preventing disease severity in individuals with breakthrough severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection.
The COVID-19 pandemic caused by SARS-CoV-2 has severely affected the global healthcare system, with more than 6.5 million deaths registered worldwide. Being a respiratory virus, SARS-CoV-2 primarily infects the upper and lower respiratory tracts. However, robust systemic inflammation is a major hallmark of severe COVID-19, leading to aberrant platelet, neutrophil, endothelial activation and blood clot formation (thrombosis).
To effectively manage the pandemic trajectory and reduce detrimental outcomes, several COVID-19 vaccines have been developed and marketed in record time and speed. In clinical trials and real-world setups, many of these vaccines have shown high efficacy in preventing SARS-CoV-2 infection, severe COVID-19, hospitalization, and death.
In individuals with breakthrough infections (contraction of SARS-CoV-2 infection despite vaccination), COVID-19 vaccines have been found to prevent disease progression and fatal outcomes. These vaccines have also been found to reduce the incidence of acute myocardial infarction, ischemic stroke, and venous thromboembolism in infected individuals.
In the current study, scientists have determined the efficacy of COVID-19 vaccines against SARS-CoV-2-induced platelet, neutrophil, and endothelial activation in hospitalized patients with breakthrough infections.
The study was conducted on 14 hospitalized COVID-19 patients who had previously received the mRNA-based vaccine developed by Pfizer/BioNTech. As an experimental control, the study included an age- and sex-matched group of 28 hospitalized COVID-19 patients who had not received any vaccination.
Peripheral venous blood samples were collected from the participants to measure blood coagulation markers and platelet, neutrophil, and endothelial activation markers. Specifically, platelet activation was measured by circulating platelet-derived microvesicles and soluble P-selectin; neutrophil activation was measured by circulating neutrophil extracellular trap biomarkers and matrix metalloproteinase-9 (MMP-19); and endothelial activation was measured by soluble vascular cell adhesion molecule-1 (sVCAM-1) and endothelial-derived microparticles.
The analysis of clinical characteristics of the participants revealed that about 17% of unvaccinated patients required intensive care unit (ICU) treatment. However, there were no such requirements among vaccinated patients. Oxygen saturation was also significantly lower among unvaccinated patients.
Thrombotic events were observed in 14% of unvaccinated and 7% of vaccinated patients during hospitalization. Death occurred in 21% of unvaccinated and 7% of vaccinated patients.
The analysis of a panel of blood parameters revealed no significant change in platelet count between the vaccinated and unvaccinated groups. Compared to healthy individuals (without infection), unvaccinated patients showed significantly higher neutrophil counts.
Both vaccinated and unvaccinated patients showed a significantly higher neutrophil-to-lymphocyte ratio compared to healthy individuals. This ratio is considered to be an index of systemic inflammation and a predictive marker of worst disease outcome.
Blood coagulation parameters
The analysis of blood coagulation parameters revealed significantly higher levels of D-dimer and fibrinogen in both vaccinated and unvaccinated patients than in healthy individuals. This highlights the association between SARS-CoV-2 infection and hypercoagulation. A significant impairment in endothelial functions was also observed in both patient groups.
The intensity of systemic inflammation and hypercoagulation was relatively lower in vaccinated patients than in unvaccinated patients.
Markers of platelet, neutrophil, and endothelial activation
The analysis of various thrombotic parameters revealed significantly lower levels of platelet and neutrophil activation markers and neutrophil degranulation markers in vaccinated patients than in unvaccinated patients.
In contrast, no significant impact of vaccination was observed on endothelial activation markers. Significantly higher levels of these markers were observed in all hospitalized COVID-19 patients compared to that in healthy individuals.
The study highlights the significance of COVID-19 vaccination in reducing infection-induced activation of platelets and neutrophils and preventing thrombotic events in hospitalized COVID-19 patients.