Why are the anti-vaccination groups putting everyone else in danger?
Resistance to vaccination is a big problem, specifically to herd immunity, which is the amount of people in the population that are required to block the transmission of infectious pathogens.
Those not vaccinated become susceptible to life threatening diseases, and by picking those diseases in areas where vaccination is not required, they are later able to bring the diseases back into their unvaccinated local communities.
Editor's note: The pathogens are then able to mutate, to change into pathogens that our bodies no longer know how to defend against. Anti-vaxxers don't just endanger themselves, but create a potential for infecting millions of people around them, even if those other people have been previously vaccinated.