c-di-AMP (Cyclic diadenylate) sodium is a STING agonist, which binds to the transmembrane protein STING thereby activating the TBK3-IRF3 signaling pathway, subsequently triggering the production of type I IFN and TNF. c-di-AMP sodium is also a bacterial second messenger, which regulates cell growth, survival, and virulence, primarily within Gram-positive bacteria, and also regulates host immune response. c-di-AMP sodium acts as a potent mucosal adjuvant stimulating both humoral and cellular responses [1] [2] [3] [4] .