I submitted my resume at the job fair, and most of them called for an interview in a few days.

Generally, I will reply you in a week or so, but I don't rule out special circumstances, such as the main person in charge is on a business trip. But if a company hasn't contacted you about a month after you submitted your resume, it's probably hopeless, because if the company recognizes you. Even if the person in charge is absent, I will contact you in advance to explain the situation. Please wait a few days, or I will tell you, and the person in charge will contact you in time when he comes back.