By Dr. Anthony Policastro
Common infections can have different symptoms depending on the age of the patient. We know that is true for things like measles, rubella, and chickenpox. All three diseases can be severe in children. However, they are more likely to be severe in adults. For example, about 25 percent of adults with measles wind up in the hospital.
Chickenpox is caused by the virus Herpes Zoster. Most people are well aware of the respiratory issues and skin issues that chickenpox causes. However, a small group of children with chickenpox can develop a brain infection known as encephalitis.
It only occurs in about one in 10,000 children who develop chickenpox. In most cases, the infection clears on its own.
Adults have slightly higher rates. About one in 2,000 infected individuals gets encephalitis. While that is still rare, it is about five times the rate for children.
They do have more severity to the encephalitis. About one in 10 adults who get it die. About half of them will have permanent neurologic symptoms afterward.
Once someone has chickenpox, the virus remains in the body. In adults, the virus can sometimes attack a nerve. When it does this, it causes pain. It causes a local rash on the skin along the path of the nerve. The name of this is Shingles.
For that reason, we have a Shingles vaccine for adults. We have known for years that it protects against Shingles itself.
However, it would make one wonder. If the virus can cause brain infection, it must be able to get to the brain. If it can later cause nerve infection, perhaps it is silent in the brain and nerves.
New studies suggest that might be true. The first Shingles vaccine was called Zostavax. It was released in 2006. It was about 50 percent effective in preventing Shingles.
In 2017, another one called Shingrix was introduced. It was over 90 percent effective in preventing Shingles. Some of us have had both of those vaccines.
Initial reviews seemed to suggest that individuals who had the vaccine had a lower risk of dementia. However, they were not formal scientific studies. They just compared groups who had the vaccine to those who did not. It was possible that those who chose not to do so had other risk factors of dementia at work. Those led them to decline the shot.
One study looked at this. It was reported in Nature in April 2025. They looked at 280,000 individuals. Those individuals who were over 80 had received the Zostavax and, because of age, were not eligible for Shingrix. Those under 80 became eligible for Shingrix and received it. The results suggested a decrease in dementia of about 20 percent in the individuals who had received Shingrix.
A similar study in Australia was published in the Journal of the American Medical Association, also in April 2025. That too showed a drop in dementia among those eligible for the vaccine compared to those who were not.
This past month, The Lancet published a third study that was done in Canada using similar criteria. They also found a drop in dementia rates.
It is not far-fetched to have a virus known to attack the brain and nerves and known to reside permanently in the body after chickenpox infection to somehow be related to dementia. The bottom line here is easy. If you are eligible for the Shingles shot, go out and get it.