"Historical evidence indicates that children less than one year old, and people with compromised immune systems or eczema, are most at risk for side effects from smallpox vaccination and should not receive the vaccine. And, because the smallpox vaccine is a live virus, a recently vaccinated person could pass the smallpox vaccine virus to a vulnerable unvaccinated person, potentially leading to death or serious illness. To prevent this, the researchers recommend that people in close contact with high-risk individuals should not be vaccinated."

I would say that kids with CAH would be okay as we can double their med’s if there is a reaction and unless they are really overtreated their immune system should be fine.  Reading this:

"Smallpox is deadly, killing as many as 30 percent of those infected. Immunization against smallpox using vaccinia, the live cowpox virus, was successful in eradicating smallpox globally by 1980. But routine vaccination in the United States was stopped in 1972 when the risk posed by the vaccine outweighed the risk of contracting smallpox."

I would say that because they actually managed to erradicate smallpox, that in that case the only deaths occuring where people who had had a live vaccine.  Hence the reason for stopping the routine vaccinations.  If there is a situation whereby smallpox is introduced again, the figures of those contracting smallpox and dying because they did not have a vaccine would rise.  In fact 30% is high really and is enough that folks need to consider getting the vaccine done for any child--especially CAH children I would have thought if anything.  When you give a vaccine to someone with a compromised immunity, I thought that it was someone that had aids or auto immune deficiency of some sort.   Our kids immune systems are fine when they get enough cortisol.