The topic of varicella zoster vaccination has come up several times this week. Probably time for a summary.
Varicella zoster, commonly called shingles is caused by the reactivation (reawakening) of chickenpox virus also called varicella zoster virus (VZV) in the distribution of a nerve root that results in a localized single-sided rash that later blisters (vesicles). The rash itself is not the problem, the pain that occurs due to nerve damage called post herpetic neuralgia can be. Post herpetic neuralgia can be very difficult to manage. This can therefore be very debilitating in the sufferer. The idea of vaccination with the shingles vaccine is to prevent or at least minimize the pain and suffering that goes along with shingles.
One does not acquire shingles from another patient with shingles. As mentioned above. Shingles is the reawakening of the chickenpox that occurred many years ago. In other words the bugs causing shingles are your own. One cannot get shingles from shingles either. But one can get chickenpox from a case of shingles.
Prior to the introduction of chickenpox vaccination, 95.5% of people 20-29 yrs of age and more than 99.6% of people 40 years of age or greater have evidence of previous chickenpox (VZV) infection. All of these persons are at risk of later developing shingles. Once one has recovered from chickenpox the virus does not leave the body. It can remain contained in parts of the nervous tissue called doral nerve root ganglia. As long as our immune system is healthy, the virus remains dormant and contained. However, if our immune system is no longer capable of watching over these prisoners, they can reawaken and lead to shingles. And through that considerable pain and suffering. Shingles develops in about 30% of people over their lifetime. The likelihood of shingles rises with every decade of life over 50. By the time we are in our 80s one in two persons may suffer from shingles. This correlates with the gradual decline in antibodies to varicella. Therefore adequate boosting of anti-varicella antibodies should help reduce the incidence of varicella reactivation.
The varicella vaccine for chickenpox is very effective in preventing primary or initial infection with varicella in children and has become part of the standard vaccination schedule. It is a live attenuated (weakened) vaccine. However when this same vaccine was used in older adults it was found to not stimulate the immune response enough to prevent shingles. Hence the zoster preparation of the vaccine though containing the same weakened live varicella virus is in 14x greater quantity that was found necessary to bring antibody response to protective levels.
Trials from zoster vaccination appear to result in a 51% reduction in the incidence of zoster with a 67% reduction in the incidence of post-herpetic neuralgia (the pain). Those that did have pain despite being vaccinated wen compared to non vaccinated did so for 21 days on average compared to 24 days respectively. The severity of pain was also less in the vaccinated group.
The vaccine is currently indicated in adults aged 60 or over and are not receiving any immunosuppressive therapy such as steroids, chemotherapy. This is a currently recommended as a one time vaccination. This is not to be used to treat active shingles or the pain from recent shingles. Some experts do recommend vaccinating persons with zoster vaccine 12 months after recovering from an episode of zoster.
Most common side effects include pain at the site of injection and occasionally vesicles can develop. No cases of transmission of live virus to other individuals has been seen.