They are possible with WhatsApp Business
If you ping me on WhatsApp, you will most likely receive an auto response. I have since been asked by several people how is it that one does that. The answer is Whatsapp Business. Its pretty much the same as WhatsApp and no, its not a paid App.
I switched to WhatsApp Business ever since its launch in early 2018, primarily owing to this auto response ability. Whatsapp Business provides you the ability to set up auto responders. WhatsApp Business also comes in handy for those having two WhatsApp numbers and inclined to have them both on the same phone.