Alterations in Laboratory Parameters Related to Disease Severity in Vaccinated Patients Against SARS-CoV-2

Coronavirus disease 2019 (COVID-19) has spread rapidly worldwide with global financial and health care systems consequences. It is already well recognized that immunization against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a precondition for blocking mutations and prevent the emergence of variants. The aim of the study was to investigate the possible relationship between COVID-19 vaccines and the commonly used disease-related blood biomarkers.

Adult patients with confirmed SARS-CoV-2 infection who were hospitalized from November 8, 2021, to December 31, 2021, were included. The retrospective study was conducted in Patras University Hospital, Greece. Two groups of patients were assessed, the ones who were previously vaccinated against SARS-CoV-2 (group A, n = 21), and those who were not (group B, n = 55). After analysis of peripheral blood, we calculated on admission day for each patient the total white blood cell (WBC), absolute lymphocytes count (ALC), absolute monocyte count, D-dimers, C-reactive protein (CRP) plasma levels, lactate dehydrogenase (LDH), ferritin, high-sensitive troponin, as well as the arterial oxygen partial pressure/fractional inspired oxygen (PO₂/FiO₂) ratio.

The median age of all patients was 65.3 ± 15.2 years old; 68.4% were men and 31.6% were women. Comorbidities were present in 51 patients (67.1%). Hypertension and diabetes were observed as the most common comorbidities (33.3%). About 72.4% of the patients were unvaccinated or have received the first dose of vaccine, and 27.6% were completely vaccinated. No statistical difference was found in the total WBC count and ALC between the two groups (group A vs. group B: 8,168.95 ± 7,584.4 vs. 8,521.9 ± 6,571.3, P = 0.848 and 3,052.1 ± 7,230.7 vs. 1,279.6 ± 1,218.6, P = 0.087). Monocytes count in both groups did not show statistical difference: group A vs. group B: 672.6 ± 384.7 vs. 637.9 ± 477.8 (P = 0.754). Similarly, no difference for D-dimers (1,348.5 ± 1,397.6 vs. 1,850.9 ± 3,877.5, P = 0.575), ferritin (1,082.8 ± 1,399.5 vs. 1,327.4 ± 1,307.8, P = 0.508), high-sensitive troponin (113.6 ± 318.1 vs. 157.5 ± 48.8, P = 0.252), and CRP (6.92 ± 4.9 vs. 7.4 ± 5.9, P = 0.732). For LDH plasma levels, the statistical difference was significant (274.2 ± 85.6 vs. 387.5 ± 223.4, P = 0.003), as well as for the PO₂/FiO₂ ratio (355.6 ± 129.7 vs. 260.5 ± 123.3, P = 0,006).

In a mixed population hospitalized for COVID-19, only LDH plasma levels and the PaO₂/FiO₂ on admission day showed statistically significant difference between vaccinated and unvaccinated patients. Although unvaccinated patients are more likely to develop severe illness, they did not express significantly higher values of commonly used plasma biomarkers such as ferritin, CRP, and D-dimers which are related to disease severity.