Assessment of Serum Levels of Vitamin D and Selected Biochemical and Hematological Parameters in Rats Post-Immunized with Inactivated COVID-19 Virus

Serum levels of vitamin D (VD) are inversely correlated with the incidence or severity of COVID-19. Our study aimed to investigate the effects of inactivated COVID-19 virus (ICoV-19) immunization on vitamin D (VD) levels, as well as biochemical and hematological parameters in adult male Sprague-Dawley rats. We randomly divided twenty rats into two groups of ten: the control group (Group I) and the ICoV-19-receiving group (Group II). We administered hydroxide aluminum (HA) and a single dose of ICoV-19 (107 TCID50 of the HB02 strain of COVID-19 virus) subcutaneously to rats in groups I and II, respectively. After three weeks (day 21), we administered booster doses to both groups. Blood samples were collected from the rats of both groups primarily for the experiment and 14 days after the second administration (35th day), and then samples were stored frozen until analysis. We found no significant differences in VD levels between the two groups on day 0, but on day 35, VD levels in group II rats had significantly decreased compared to group I rats (P<0.05). Additionally, group II rats had higher concentrations of fibrinogen, blood urea nitrogen (BUN), creatinine (Cr), and lactate dehydrogenase activity (LDH) than group I rats (P<0.05). Group II rats also showed a significant increase in neutrophils (N %) and neutrophils to lymphocytes ratio (N/L) after 35 days (P<0.05), while lymphocytes (L %) decreased. These findings suggest that vitamin D may play a role in preventing COVID-19 and be a potential candidate for managing and controlling of the disease.