It is fetal tissue from, IIRC, an aborted baby, and “they” keep cloning that cell line.
Whatever the hell that means.
The CDC has a complete list of ingredients in every vaccine, it does not state whether the human stuff is from an aborted baby or not. There are horrible ingredients including all kinds of animal blood, organ tissues etc from cows, monkeys, dogs etc. As well as preservatives and so on and so forth.
I’ve heard something about that, but can make no claims about having researched it much.