How can chickenpox be prevented?
Chickenpox vaccine is available that gives protection. Also, studies suggest that the incidence of herpes zoster in vaccinated persons is much less than that in unvaccinated persons. This varicella vaccine can be given to anyone who is 12 months and above. One dose is usually enough. For children more than 13 years of age, 2 doses are recommended. The vaccine is recommended for those children who have not had chickenpox in the past.

My daughter has chickenpox. How can I make sure that my son does not get it?
Your son if he is more than 1 years of age can be given the chickenpox vaccine provided your daughter has symptoms not more than 3-5 days. It may not completely protect but may prevent severe disease if he also develops chickenpox. Also varicella zoster immunoglobulin can be given. Consult your doctor for the same.