When working with food, personal items such as cell phone should be kept away from where food is stored and prepared.
The answer is a frequency, intensity, time, and type
This is hazardous for children, especially younger children, because they are a choking hazard if they put the toy prices in their mouths and choke. What I would say to the parent is to maybe see the age range for the toy and think about if that toy is for children.
So its acquired immunity and the cells responsible are the B lymphocytes that produces antibodies against the virus. Memory is keep since first encounter of the virus by the immune system by way of the antibodies that was initially produced. The antibodies are there already, which makes it fast to act upon when expose again.