significant pockets of society opting out of vaccination:
outbreaks.
This is my concern for undocumented immigrants.
...the "personal choice" crowd and vaccines.... their personal choices can make other people, like babies, cancer patients, and people with allergies, sick or very sick.
We also have things like DTaP as an alternative to DTP (a vaccine which resulted in some claims). There may be a fine balance between accommodating individual liberties and the needs of society as a whole. This is one reason we have both the practice of individual health care, and also the CDC and field of public health.
While washing hands does not prevent all diseases, it may be something we can all agree on.
