This is one of the many dangers of mRNA tech. It can instruct the target cells to produce almost any compound a living thing can produce, including prions. Because it's produced inside the body, it can't be detected in the injection itself. It's an untraceable poison delivery system. These people were probably targeted with custom, lethal batches. The fast onset is probably the result of damage to the RNA pre-injection. Who knows how many other people are out there with ticking time bombs in their cells. The normal progression of Creutzfeldt-Jakob disease can take years.