A chain is only as strong as it's weakest link (Excuse the cliché), and the same goes for immunity of certain diseases like Whooping Cough. Without people being forced to take vaccines, you will have the people who believe vaccines are bad, they won't take them and will compromise the safety of everyone else.
What could be done in a free society to potentially solve this dilemma? Thanks!
My apologies, I just realised this has been asked before:
https://board.freedomainradio.com/topic/40336-herd-immunity/
I would delete this thread but I don't know how.