This. This is how you kill people. Not by the baby's parents doing something wrong, but by the fact that (1) babies aren't yet vaccinated, so they depend on low transmission rates in the community, and (2) other members of the community can't be vaccinated, or the vaccine was not 100% effective for them, so they too depend on low transmission rates. My son was fully vaxxed, but came down with pertussis in high school. He was fine, but it was no fun. And the doc explained that yeah, a very small percentage of vaccinated folks still get it, so herd immunity is really important.
Especially with respect to diseases that are subject to vaccines that truly reduce the hell out of transmission (pertussis, smallpox, measles, and others), herd immunity is the goal and the key. And the "fuck you, don't tell me what to do, I did my research and take colloidal silver instead" ethos that doesn't just exist, but is now official US policy, is already killing people and will kill many more.