Darwin's suggestion anticipates phylogenetic bracketing, a method based on that uses characteristics of organisms in a clade to make predictions about the common ancestor of the clade and all of its descendants.

Vaccines train our immune systems to create proteins that fight disease, known as ‘antibodies’, just as would happen when we are exposed to a disease but – crucially – vaccines work without making us sick

Explanation:

mRNA Vaccines Are New, But Not Unknown

This means the process can be standardized and scaled up, making vaccine development faster than traditional methods of making vaccines. mRNA vaccines have been studied before for flu, Zika, rabies, and cytomegalovirus (CMV).