Hemophagocytic lymphohistiocytosis and SARS-CoV-2 vaccination.

Dear Editor, we would like to share ideas on the publication “Hemophagocytic lymphohistiocytosis (HLH) after SARS-CoV-2 vaccination [1].” Hieber et al. mentioned that “COVID-19 vaccines may occasionally trigger HLH, and Anakinra may be an efficacious treatment option for this condition [1].” The COVID-19 vaccines can cause unwanted adverse effect and HLH might be a clinical adverse effect. In the present case, the patient had HLH. However, there are no data on pre-vaccination immune/health status of this case. The HLH might or might not be an adverse effect of the COVID-19 vaccine. The possibility of a concurrent medical problem should be discussed. For example, dengue is a possible concurrent medical problem [2] and HLH might be the complication of dengue infection [3].