Girls, can you tell me if there are any methods to prevent a child fro…

Girls, can you tell me if there are any methods to prevent a child from getting sick? I'm going on sick leave once a month. And now at the beginning of the month - twice in the morning she coughed and heard as if inflammation in the throat, like hoarseness. At the same time, the voice is normal. I immediately treated it with Miramistin. The doctor gave me some medicine. But I think all this is useless ? There's no fever yet. What can I give, do, to avoid illness...