My theory is its intentionally a slow burn. Effects dispersed over years for most. Some die in the first year,some develop serious conditions and die over another couple years,those who dont die are crippled and the unscathed jabbed and purebloods are too overwhelmed caring for them to revolt in any meaningful way. My guess is it might take five to ten years for full effect,and my other guess is they needed perpetual boosters to ensure this--which is why the push for self a bolstering jabs with saRNA. They found out most people will willingly or forcibly take the first jab but won't willingly take boosters four or more times a year ad infinitim, so now they're developing a way to relieve you of the right to make that choice after you took that first poison dose to save your job. Once you commit to one jab, you are committed to eternal boosters,whether you get jabbed or not.

Edit to add: Even better than hiding the damage while making even more profit treating the symptoms, by dispersing the damage over years (divide and conquer), the relatives of the victims will be on the hook for body disposal. Kill too many too fast you may have a corpse disposal problem.