There still seems to be a lot of confusion about shingles and it seems a good time to write about it again.
Shingles and chicken pox are caused by the same virus known as varicella/zoster. Normally, children catch the virus at a young age and develop chicken pox, which can vary from an itchy spotty disease to an asymptomatic attack. In the immunodeficient it can cause a severe and often fatal viral pneumonia. Most people rapidly recover from chicken pox, but the virus remains in the body hidden in one or more nerve cells in the spine.
In the elderly and especially in the immune deficient the virus can be reactivated and migrate down a peripheral nerve to cause a painful blistering rash over the skin where the nerve supplies sensation. This is called shingles. Very occasionally in the immunodeficient there are recurrent attacks, not necessarily in the same nerve, and even more occasionally in the very immunodeficient the virus can disseminate causing chicken pox which may be fatal.
A little while ago a vaccine made from attenuated live virus was developed and used to prevent chicken pox in children in some countries (though not in the UK). This same vaccine is offered to older people to prevent shingles. CLL experts have determined that as it is a live vaccine it should not be given to CLL patients, although small numbers have had it safely.
It needs to be stated clearly that normal people do not catch shingles from people with chicken pox, although children can catch chicken pox from adults with shingles.
There is an unanswered question. Do patients with CLL have enough anti-zoster immunity to withstand a fresh attack of the virus, either from someone with chicken pox or zoster who is excreting the virus, or from someone who has been vaccinated and is excreting the attenuated virus? The answer to that question is that we don't know. Clearly some do have enough immunity, even though they may have no zoster antibodies. I would suspect that CLL patients are more at risk from the virus living inside them than from a virus that someone else is shedding which may never gain entry to their bodies.
What advice can we give? Obviously the safest advice is to quarantine yourself from anyone who may be shedding virus, this means until the blisters have healed up. Unfortunately, this is not always practical. If it is not, then the next best advice is to take prophylactic aciclovir or equivalent. The good news is that almost all cases of varicella/zoster infection respond to these drugs.