COVID-19 vaccination, anticoagulation level and warfarin treatment

Dear Sir,

We would like to share ideas on the publication “Anti-SARS-CoV-2 vaccination does not influence anticoagulation levels in stable long-term warfarin treatment”¹. Lotti et al. concluded that “No influence on the quality of OAT was detected … thus confirming the stability of anticoagulation levels”¹. We agree that the interaction between COVID-19 and warfarin is an interesting issue. Conceptually, if there is a linked biomechanism, there should be an interaction. Based on available evidence, there is no biological process of the immunogenesis by COVID-19 that is linked to the pharmacological action of warfarin. Therefore, there should be no interference. However, an important consideration can be made. Although there is no direct interaction between the vaccine and warfarin, it could be questioned whether there is any laboratory interference from the vaccine. Basically, after vaccination, there will be an increase in the level of immunoglobulins, which might result in high blood viscosity². An aberrant high level of immunoglobulins could potentially interfere with the basic analysis of coagulation profiles. Indeed, there is a report that point-of-care coagulation profile monitoring is affected in cases with abnormal immunity and that careful interpretation of results is necessary³.