What did the women mean when she said "they're the only ones keeping the monsters away"?

In chapter 54 page 262 at the bottom of the page, a women says to Alec and Mark "no need to take my kids. They're the only things keeping the monsters away". What did she mean by this, how are the keeping the 'monsters' (the people who are injecting them) away?? Is it because they are scary? Or is she giving them away? Or do they not target kids? Maybe something else? Thanks