It is only possible to have one episode of the disease.
Persons with leukemia are at higher risk.
Persons of all ages should receive the zoster vaccine (Zostavax).
Persons between 30 and 40 years old are at high risk.
Number 2 is correct.
Persons with suppressed or compromised immune systems, such as occurs with leukemia, are at higher risk to acquire shingles. Although rare, a second and even third episode of shingles can occur. A zoster vaccine is recommended for persons 60 years and older, the timeline for highest risk of acquiring herpes zoster.