There is a huge disconnect in health care providers and families alike, and the health organizations' (i.e. CDC) on safe handling of formula. Although there is plenty of information out there on risks of poor handling/prep, life-threatening issues, and easy-to-follow steps, one does not know to look for it if its not talked about.
In my humble opinion, it is negligent on the health care professional's side to recommend formula use without taking the time to talk proper preparation beyond just how much to mix in. Yes, parts can be found on packaging, but when dealing with the health and safety of an infant, we shouldn't be so reliant on product packaging. Anything and everything that could be given to an infant will say, "Consult with doctor" or "Ask the doctor," yet formula is not part of that urgency.
Formula found in the forms of powder and concentrate are NOT sterile, and actually have an allowed threshold of bacteria while on the shelf. Once water is added to a dehydrated or stagnant organism, it springs life and ability to multiply back into it. This is why mixing sterile water while still hot from boiling is a crucial step missed in this scenario all too often. We even see products on the market to make it even easier to mix formula, and the temperatures do not reach bacteria-killing temperatures. This is when we have issues in infants, such as diarrhea, seizures, gas, sepsis, urinary tract infections, and more.
How long should these steps be taken? At least the first 6 months of the infant's life, due to his/her developing immune system. Though I still recommend it throughout the entire time using formula.
Here is my comprehensive infographic on formula preparation, along with the main resources I have for the information provided. I hope this helps those who need it!