CD4 and systemic lupus erythematosus: It has been reported that the application of mRNA or DNA vaccines against the coronavirus disease (COVID-19) has been shown capable of causing new or relapsed onset of SLE.253–256 A boost in spike protein-specific CD4+ Th1 and CD8+ T cell responses were detected after the use of AZD1222 (i.e., a DNA COVID-19 vaccine),257 the mechanism of which could be attributed to activated TLRs followed by induced type I IFNs-mediated signaling.