A Comparison of Plasmid DNA and mRNA as Vaccine Technologies

Liu, Margaret A.

DNA vaccines as a manufactured entity are noted for their stability [25] , particularly when supercoiled. As noted above, this stability is reflected even in vivo, since plasmid has been detected in a non-integrated form in muscle up to six months following injection [18] . Although the ubiquity of RNAses with the resulting instability of native mRNA has been a significant reason for the delay in development of mRNA, the actual manufactured mRNA is stable in liquid or lyophilized form, (reported to be stable up to two years at room temperature [26] ) with an inverse relationship of stability to temperature. It has been reported that a rabies mRNA vaccine was still effective for pre-clinical protection after several months at temperatures ranging from −80 • C to as high as +70 • C [26] . The stability of mRNA as a vialed product (i.e., protected from RNAses) is a separate consideration from the stability in vivo, and any formulations or delivery devices (which may cause shearing during delivery) are key factors in the final stability as a delivered product.