Chickenpox Vaccine and Shingles Risk
When I was 4 or 5 years old, in the early 1980s, I contracted chickenpox (also known as varicella). I remember the days that I spent home feeling sick and covered in pocks because my parents decided that it would be a good idea to invite all my cousins to come over and get exposed. The house was soon filled with over a dozen children my age, and I couldn’t join them in playing because I was sick while they were running around, laughing and playing. A few days later, I felt better, but almost all of my cousins went down with the disease.
One of them suffered severe consequences from the chickenpox infection they contracted from me. According to the Centers for Disease Control and Prevention (CDC), chickenpox infection can cause a range of complications, including bacterial infections, pneumonia and encephalitis. While these complications are rare — leading to the assumption that chickenpox infection is somehow “benign” — they are avoidable given the very effective chickenpox vaccine. The varicella vaccine has an excellent safety track record, and has been largely successful in making chickenpox in the United States a disease that not a lot of healthcare providers treat as it is estimated by CDC that up to 3.5 million cases of chickenpox are prevented each year with the vaccine.
Those of us who contracted chickenpox “the natural way” are at increased risk of shingles (also known as “Zoster” or “Herpes Zoster”). This is because the varicella virus becomes dormant after a natural infection, embedding itself in the nerves near the spinal cord. Before the vaccine was available, people contracting chickenpox would fight it off to the point of making the virus dormant. Almost every year, a person would have their immune system “boosted” when they came into contact with a person (usually a child) with chickenpox. That boosting effect would make sure that the dormant virus remained so.
It used to be that people who contracted chickenpox as children and then would later develop some immune-compromising disease or condition would be at highest risk for shingles. This is because their immune system would be compromised and unable to keep the virus at bay if it “awoke” from being dormant. Because of the high effectiveness of the vaccine, those of us who had the infection are no longer being boosted because we don’t come into contact with children with the disease as often, if at all. As we grow older, the dormant virus may become active. Because we haven’t been boosted, there are less memory cells left to remember how to fight off the infection.
This leads to the skin condition known as shingles. Shingles is a painful skin rash, usually on one side of the body, that scabs over in a few days and clears up in a couple of weeks. It is painful because the virus causes damage to the nerves where it was dormant. In some cases, complications similar to those caused by chickenpox can happen. To prevent shingles, there is a Zoster vaccine recommended for people over the age of 60, though more and more evidence is coming to light that it may be necessary to lower that age recommendation because less and less adults are being boosted, leading to lower ages where the virus is reactivated and a wider gap since the last time their immune system confronted the infection.
This week, new evidence was published showing that children who receive the two recommended doses of the chickenpox vaccine are less likely to develop shingles later in life. This makes sense since these children are given the same immunity a natural infection would give, but they are given a weakened version of the varicella virus. That virus has almost no chance of surviving its encounter with a healthy immune system, so it does not cause disease, does not go dormant in nerves and it triggers enough of an immune response to protect children from infection for the future.
In the United States, we are going to have to deal with the epidemiological transition of chickenpox in children going away while shingles cases increase in adults. While we are preventing a potentially deadly infection, we are transitioning the burden of Varicella zoster to older populations. With more and more Americans living well into their 80s, and more living longer with immune-compromising conditions like cancer or HIV, the shingles vaccine recommendation is going to have to be reviewed soon. Then there’s the matter of shingles vaccine supply, but that’s for a different blog post at a later time.