As anyone who has had shingles knows, it is a painful and often debilitating infection that may last for weeks or months. A particularly troubling type of this infection is herpes zoster ophthalmicus (HZO), or shingles of the eye. It may lead to serious eye problems including blindness and is considered an ophthalmologic emergency. Researchers have been concerned about the rising incidence of shingles and HZO. HZO increased from 10 cases per 100,000 population in 2004 to 30 cases per 100,000 in 2016. No other disease has tripled in incidence in 12 years. Initially, researchers chalked up the rising incidence to the aging of the population, but that does not really explain the huge jump in numbers of cases. In addition, the increase in cases is seen mostly in white women and not in white men, blacks, Asians and Latinos. This too cannot be explained. Recently, an interesting theory was proposed.
Shingles is caused by the varicella zoster virus, the same virus that causes chickenpox. Almost all adults over 40 have immunity to the virus because they had chickenpox or were exposed to it. This immunity wanes over time, however. In 1995, the varicella vaccine was introduced and the number of chickenpox cases in the U.S. dropped dramatically. It is important to note, however, that immunity from vaccination is usually weaker than immunity from disease. One theory is that because the number of chickenpox cases has dropped so dramatically, immunity in adults has also dropped. In other words, when children get sick, they are cared for by their parents. Because of this, disease exposure in adults causes an immune system boost. In short, the parents caring for their sick children got an immune system boost from exposure to their child’s disease. But since childhood chickenpox is now rare, the parents’ immune systems don’t get that boost anymore.
Another factor in the rising rates of shingles and HZO is the low rate of adult shingles vaccination. The Centers for Disease Control (CDC) reported in 2016 that only about 33 percent of adults over 50 had been vaccinated with Zostavax. Zostavax was licensed in 2006 for use in adults over 50 (although most insurance plans will not cover it until age 60). Shingrix, a more effective vaccine for shingles, was licensed in 2017 and is approved for adults over 50, although it requires two doses and is usually more expensive than Zostavax. Many primary care providers do not stock either vaccine because they are so expensive. Patients are given a prescription for the vaccine and sent to a pharmacy.
The CDC estimates that each year about one million Americans develop shingles and the rate is rising. In 1945 through 1949, the incidence of shingles was 0.76 cases per 1000 person-years, and from 2000 through 2007 the rate was 3.15 per 1000, a four-fold increase. About 20 percent of persons with shingles will develop HZO. In addition, post-herpetic neuralgia, a painful condition that may follow a shingles infection and can last for years, occurs in 10 to 30 percent of those with HZO as opposed to less than 13 percent of those with shingles in other body areas. So, this year, if you have not already received it, ask your doctor about shingles vaccination the next time you go for a checkup.
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