Also, it helps to mostly kill old people who are already sick. It makes it much harder for people to notice. Your drug might have killed them, but chances are

Also, it helps to mostly kill old people who are already sick. It makes it much harder for people to notice. Your drug might have killed them, but chances are they were going to die in the next 6 months anyway so the death didn't stand out. It also makes the death toll hard to tally.