De rigueur pointer to a discussion of the birthday paradox for those who don't understand why the combination of first name, last name, and birth date is an unavoidably flawed way of uniquely identifying individuals: https://www.scientificamerican.com/article/bring-science-hom... .
Personal anecdote: my parents used a pediatrician who identified minor patients by first + last + birth month. The office had to start using middle initial as well to disambiguate me from another patient.
She hadn't even seen the doctor in question for more than 9 months, had never had any indication of the problems in question (but had had tests done that could have identified such) and was generally thoroughly freaked out by this. Turns out the practice had another patient with the same name and was just a little sloppy about which person got called.