The most common age of polio is 4 months to 5 years old, mainly because babies under 4 months old are more protected by maternal antibodies, and then the antibodies from the mother will decrease after more than 4 months, and after 5 years old, mainly because babies grow up and become stronger, and they will produce certain antibodies by themselves. Therefore, between the age of 4 months and 5 years, the resistance is on the low side. Moreover, babies in this age group love to eat, have a wider range of activities, and are prone to come into contact with virus-contaminated toys, food, and water, or accidentally come into contact with someone who is already infected, or consume infected things.