An advanced bio weapons lab scientist finds a new way (mRNA) to alter a population's DNA via a highly contagious virus. The scientist believes that there are “bad genes” in the human population and wants to eliminate a whole segment of the population. The plan is to release a highly contagious but not very lethal virus that forces a great majority of the population to get a vaccine.
But the scientist does not release the actual DNA of the virus for others to develop the vaccine. Instead, the release code is designed to create viruses that are future enablers of other illnesses. A couple of “mutations” cause the population to accept these new mRNA vaccines.
This sets up several possibilities that include release of a new virus that reduces reproduction rates, or causes cancers to be more prevalent. It would take some time for the corelation to work its way back to the virus, but by then, it would be too late