[Joeri]

If vaccination rates are too low you don’t get herd immunity, and people who are unable to be vaccinated are more at risk.

[pmdulaney]

What is a typical reason someone wouldn't be able to be vaccinated?

[barabba]

https://en.m.wikipedia.org/wiki/Immunosuppression

  Non-deliberate immunosuppression can occur in, for example, ataxia–telangiectasia, complement deficiencies, many types of cancer, and certain chronic infections such as human immunodeficiency virus (HIV).

[_qwfv]

https://www.cdc.gov/vaccines/vpd/should-not-vacc.html

It varies by vaccine, but allergies, health conditions, and age are all factors.

Some people also practice religions that forbid them.

[johne20]

One example, babies too young to receive vaccines or pregnant mothers.