Childhood Shingles Resulting from Chickenpox Vaccination: “Rare” or Predictable?
From the inception of mass vaccination, childhood vaccines have produced a raft of unintended consequences. One of the biggest problems—gaining steam over the past several decades—involves the vaccine-induced creation of brand-new risks and vulnerabilities that can be more serious than the condition a given vaccine might be intended to address.
The varicella (chickenpox) vaccine represents a case in point. Chickenpox, usually mild when experienced in childhood, was once a routine rite of passage. After the rollout of universal varicella vaccination, the incidence of chickenpox declined but observers began noticing a “’perverse’ boom” in shingles (also called herpes zoster). Chickenpox and shingles infections both stem from varicella zoster virus—and before the advent of the varicella vaccine, children infected with chickenpox helped boost adults’ immunity to shingles by inhibiting the latent virus’s reactivation. Chickenpox vaccination disrupted this intergenerational protective mechanism, not only eliminating regular boosting for adults but shifting downward the average age at which shingles occurs. In addition , because varicella vaccine-induced immunity decreases by 8% with each year since vaccination, previously vaccinated young adults are at increased risk for varicella outbreaks and potential complications later in life. In short, while the reduced circulation of wild chickenpox virus may spare some healthy children a benign case of chickenpox, children now face the more serious risk of developing shingles at young ages and chickenpox at older ages.
Predictions and case reports
When the Centers for Disease Control and Prevention (CDC) added first one and then two doses of chickenpox vaccine to the U.S. vaccine schedule (in 1996 and 2006, respectively), numerous scientists predicted—accurately as things have turned out—that there would be a chickenpox-shingles tradeoff. In fact, the United Kingdom does not include the varicella vaccine in its childhood schedule to this day precisely because researchers there recognized the potential for routine chickenpox vaccination to “drive up the age at which those who are non immune get the illness” and increase the incidence of shingles in all age groups. Confirming the initial predictions, the incidence of shingles in the U.S. rose by 63% among 10- to 19-year-olds as of the mid-2000s.
Ordinarily, clinicians do not expect to encounter shingles in children unless the children are seriously immunocompromised. Perhaps this is why—in one case report after another describing shingles in otherwise healthy vaccinated children—researchers characterize the situation as “rare” or “unique.” Even so, young shingles patients’ often dramatic clinical symptoms have forced researchers to acknowledge that shingles is definitely “possible” in children vaccinated against varicella, and when they use appropriate molecular analyses, they find that the vaccine-strain virus is the causative agent.
In 2017, clinicians encountered shingles in a healthy 19-month-old who had received a chickenpox vaccine six months previously, and they decided to put their findings in context by searching the English-language literature for similar cases. They identified roughly two dozen published cases of vaccine-strain shingles in “immunocompetent” children and adolescents who had received a chickenpox vaccine but otherwise had “no history of varicella or exposure to varicella during gestation.” A number of the studies reported shingles in very young children—such as a 15-month-old vaccinated three months previously, a 2-year-old “vaccinated for varicella at 17 months,” another vaccinated 2-year-old, and a 3.5-year-old girl who had received the chickenpox vaccine around age 2. Across studies, the average age of shingles infection in children was 5.3 years, and the infection surfaced, on average, about three years after chickenpox vaccination.
Adverse events and complications
Young shingles patients experience a wide range of “rare but important adverse events.” Case reports have described:
- Lesions on the forehead, nasal bridge and upper and lower eyelids of a “previously healthy” 6-year-old boy who received the chickenpox vaccine at 1 year of age.
- Persistent shingles-related eye complications in a 6-year-old girl “with no medical history” who had been given two doses of chickenpox vaccine (at age 1 and again one year prior to the onset of symptoms).
- Headache, eye pain, eyelid rash and other symptoms in a 7-year-old boy who was “otherwise healthy and had received all of his scheduled vaccinations.”
- Ocular herpes zoster lesions and nerve palsy in an 8-year-old boy with “up-to-date immunizations” and an “unremarkable” medical history.
Unfortunately, shingles carries the risk of even more serious complications, including the vision-threatening eye condition called herpes zoster ophthalmicus—experienced by up to one in four persons with shingles. In a case series reporting shingles in seven “immunized healthy children without underlying immunodeficiency,” researchers described severe lesions as well as upper respiratory symptoms and joint pain. Other major complications that may occur either in tandem with rash or on their own include central nervous system problems such as encephalitis and meningitis. A 19-year-old female college student who had received two prior doses of varicella vaccine developed shingles-related encephalitis that landed her in intensive care and resulted in lengthy hospitalization. The strong antiviral drugs used to treat these conditions can cause kidney dysfunction. Mayo Clinic researchers report that asthma and atopic dermatitis both are associated with a higher risk of shingles.
The “cost of success”?
Researchers at the University of British Columbia have suggested that vaccine-associated shingles complications are just “one of the costs” of the “success” achieved with universal chickenpox vaccination. However, given that one in five children who receives the varicella vaccine develops a “breakthrough” chickenpox infection anyway, just what kind of “success” are we talking about? In fact, “in communities with high vaccination coverage, varicella cases mostly occur in vaccinated individuals.” At the same time, because the varicella vaccine is a live virus vaccine, “[p]eople who get chickenpox vaccines can spread the vaccine-strain varicella-zoster-virus to others,” a troublesome fact quietly acknowledged on the CDC’s website. When those “others” are young adults or older, the cases not infrequently result in serious complications. Finally, it should be noted that, as is the case with nearly all vaccines on the market, the FDA approved varicella vaccines without any long-term safety testing—the vaccines received a scant 42 days at most of monitoring after a single dose of vaccine.
In 2010, CDC researchers identified yet another concern when they reported that their laboratory had observed—in about 11% of the adverse events resulting from varicella vaccination—“recombination between vaccine and wild-type [varicella zoster virus] strains.” Moreover, the “recombinants” demonstrated “a selective preference for reactivation, enhanced replication, and/or an enhanced ability to traverse the nerve.” The World Health Organization and other bodies have acknowledged that this type of vaccine-plus-wild-virus recombination raises “unique safety issues.” The CDC researchers noted that the shingles vaccines it now recommends for older adults (“formulated at a virus concentration more than 14-fold higher than that of childhood varicella vaccine”) are likely to “substantially” increase the occurrence of “vaccine-wild-type recombination.”
Chickenpox vaccines are far from the only type of vaccine to give rise to unintended consequences. In a recent commentary, a leading pertussis expert admitted, for instance, that pertussis vaccination actually increases vaccinated individuals’ lifetime susceptibility to pertussis. Merck’s highly flawed measles-mumps-rubella (MMR) vaccine (which relied on faked data to achieve Food and Drug Administration approval) has likewise backfired, prompting rampant fertility-threatening mumps outbreaks in young adults. It is time to bring “unintended” consequences out into the open and make sure they factor into all assessments of vaccine safety and efficacy.