At some point in the early 1980s, a young and slightly less cynical me developed fever and malaise that was soon followed by a generalized rash consisting of small red bumps. These lesions quickly evolved into small blisters. I stayed home from school for a few days while several new “crops” of bumps and subsequent blisters would emerge and then ultimately crust over. I remember not feeling particularly ill after the initial prodrome ended, but the itch was intense.

Within a week I had stopped developing new lesions and was covered in the crusted remnants of the disease, which I am confident that the vast majority of readers will recognize as chickenpox, more formally known as varicella. Varicella is the classic and formerly ubiquitous childhood manifestation of primary infection with the varicella-zoster virus (VZV). My case was very typical of childhood infection in that it was relatively minor and resolved without any permanent sequelae. Even the scars that for years served as a reminder of particularly itchy areas are now long gone.

The majority of cases of varicella, then and now, were similar to mine. Because of this, and the fact that severe complications weren’t common, most people who are old enough to have had the disease remember it as an annoying childhood rite of passage. I certainly didn’t live in fear of chickenpox like my parents, and earlier generations, did of other vaccine preventable diseases.

But varicella wasn’t benign for many people, especially those with compromised immune systems, and it had significant economic costs. Yet there is no shortage of anti-vaccine activists claiming that the vaccine is harmful and that the disease is harmless, sometimes qualifying this claim with “in healthy children” despite the fact that most severe cases occurred in just that population. They believe that natural immunity is better than “synthetic”, whatever that means. And many hesitant parents who I would not lump into the anti-vaccine camp question the necessity of this vaccine as well.

But before I discuss a case report that provides an unfortunate example of why avoiding the varicella vaccine is a terrible idea…

A brief primer on varicella

As mentioned above, varicella is the typically childhood presentation of primary infection with the varicella-zoster virus (VZV). It is never cleared from the body, instead finding nooks and crannies in the central nervous system where it lies dormant. Reactivation of the virus, usually decades later, is commonly referred to as herpes zoster, zoster, or shingles. Although not the focus of this post, there is also a vaccine offered to individuals over 50 years of age which can significantly reduce the risk of shingles outbreaks.

Prior to the development and widespread implementation of a safe and extremely effective vaccine against the development of varicella, the highly contagious virus (> 90% of non-immune close contacts become ill) affected more than 95% of people in the United States before their 20th birthday, with roughly 4 million cases annually. Children, particularly those under the age of 10 years, were by far the most likely to become infected. Of these cases, around 11,000 required admission to a hospital, 80% of which involved healthy kids. Of the more severe presentations each year, about 100 people died.

Young infants, and the small number of unlucky adults, who developed primary varicella infection were, and are, the most likely to develop severe disease. To put this into perspective, adults made up 5% of cases each year prior to the vaccine but more than half of the deaths, most commonly as a result of severe inflammation of the lungs or pneumonia. Infants accounted for a large chunk of the remaining fatalities, with secondary bacterial infections and pneumonia being the more common causes of severe morbidity and mortality.

In addition to bacterial skin infections and pneumonitis/pneumonia, one of the most dreaded complications of varicella involves the central nervous system. Inflammation of the brain, known and encephalitis, historically accounted for about 20% of hospital admissions. In children, isolated inflammation of the cerebellum was common. Though seen more in adults, infants are at increased risk of diffuse inflammation of the brain, which can cause altered mental status, seizures, stroke, and death.

The varicella vaccine protects children

The varicella vaccine was first rolled out in 1995 and it has been a tremendous success. Initially only one dose was recommended for children 12 to 15 months of age, older kids who had not had the disease yet, and people with risk factors for severe infection. Within just a few years, the number of cases plummeted by over 70%. By 2005, the drop was 90%. There were also far fewer cases in the adult population, because herd immunity is a wonderful thing.

Despite these clear improvements, and despite more than 90% of children receiving the vaccine, the decline in cases plateaued. Because no vaccine is perfect, about 25% of vaccinated children were not developing immunity and there were outbreaks even among highly vaccinated populations. Disease tended to be milder than in the unvaccinated population, however. In 2006, the ACIP recommended a booster dose to be given at 4-6 years of age, which decreased the incidence of varicella by another 80% or so.

Currently only about 4 out of every 100,000 people will develop varicella in the United States. In addition to this, those who develop disease despite being vaccinated are very unlikely to have severe complications. Of course this will all go away if vaccination rates fall low enough.

Varicella-associated stroke in an 11-month-old child

A case report was published in the September issue of The Journal of Pediatrics that serves as a good example of why varicella should not be shrugged off as just a minor childhood illness. It also highlights the importance of the vaccination in protecting those that are too young to have received it.

In the report, the authors describe the case of an 11-month-old boy who presented to Seattle Children’s Hospital with the sudden onset of weakness involving the right side of his body. He was found on MRA to have a left middle cerebral artery stroke and signs of vasculopathy. It was then discovered that the patient, as well as his older siblings, had varicella 2-3 months prior that had seemingly resolved without incident.

Vasculopathy in the brain is a known complication of varicella, can develop weeks after the infection seemingly resolves, and is more common in children under the age of 1 year. Because of the possibility that VZV infection was to blame, and the fact that early treatment can improve outcomes, he was empirically started on an antiviral medication while spinal fluid studies were pending.

He was ultimately found to have VZV DNA in his spinal fluid and blood tests confirmed an immune response consistent with a recent infection. His weakness eventually improved, however follow-up imaging showed worsening of his vasculopathy with involvement of additional vessels. This may portend additional neurologic difficulties down the road.

Not discussed in the brief case report were any details regarding why this child’s older siblings had varicella. Did they catch it first and spread it to the baby, or were they all exposed at the same time? An 11-month-old is too young to be vaccinated, but his older siblings aren’t. It isn’t clear if they were not vaccinated because of choice or legitimate contraindication, the latter being very unlikely.

I’m curious where they were exposed to VZV. Was it a “pox party”? Do they attend a school full of the children of hesitant or anti-vaccine parents? Seattle is one of the “hot spots” of low vaccine rates that I wrote about a few weeks ago, after all.

Conclusion: Vaccinate your kids…please

I won’t lie and say that varicella infection is as scary as the measles or HiB meningitis, but it can cause suffering and even death. Thankfully we hardly see it anymore these days. I haven’t seen a case in 15 years. The varicella vaccine is safe and it is very effective when administered as recommended by the ACIP and the AAP. So unless there is a clear contraindication, there really is no legitimate excuse to skip it.


Posted by Clay Jones

Clay Jones, M.D. is a pediatrician and a regular contributor to the Science-Based Medicine blog. He primarily cares for healthy newborns and hospitalized children, and devotes his full time to educating pediatric residents and medical students. Dr. Jones first became aware of and interested in the incursion of pseudoscience into his chosen profession while completing his pediatric residency at Vanderbilt Children’s Hospital a decade ago. He has since focused his efforts on teaching the application of critical thinking and scientific skepticism to the practice of pediatric medicine. Dr. Jones has no conflicts of interest to disclose and no ties to the pharmaceutical industry. He can be found on Twitter as @SBMPediatrics and is the co-host of The Prism Podcast with fellow SBM contributor Grant Ritchey. The comments expressed by Dr. Jones are his own and do not represent the views or opinions of Newton-Wellesley Hospital or its administration.