Generation at risk: Why Are Ever-younger Adults Contracting Shingles?
"Natalie" was about to start teacher's college in Toronto when her left eyelid began burning and stinging. "I thought the pain was from a new eye-makeup remover I was using," she remembers. When the irritation did not subside, she went to see her doctor. The diagnosis: shingles.
Also known as herpes zoster, shingles happen when the virus that causes chicken pox, varicella zoster, is reactivated. Long after the itchy, red bumps associated with chicken pox disappear, the VIRUS that caused them remains dormant in the body, hiding in the nerve cells along the spinal cord. The virus can then resurface later in life as shingles - sometimes in otherwise healthy people, more often in those with weakened immune systems, such as the elderly. But shingles appears poised to become an equal-opportunity DISEASE, infecting ever-younger adults. The reason, experts say, is that vaccines have, paradoxically, rendered an unlucky cohort more vulnerable.
Natalie was just 24 years old when she got shingles and she had a particularly stubborn case. Valtrex, an antiviral, didn't help. The itchy rash spread across her forehead and into her scalp, and then, for about four weeks, she couldn't open her eye. "I was in such severe pain I thought I was going to go crazy," she recalls. At night, she'd lie on the floor, crying, unable to sleep because the burning, itching sensation was so excruciating. A doctor prescribed antidepressants for a month to numb the nerve pain - and warned that some patients with shingles in the nerves around the eye found the burning and itching so unbearable, they killed themselves.
Three years later, Natalie is "still dealing with the aftermath." While she had perfect vision pre-shingles, she now has light sensitivity due to permanent scarring of the cornea, and can't wear glasses because her eyesight changes depending how the virus affects her cornea at a given time. She also suffers from post-herpetic neuralgia, the prolonged and sometimes debilitating nerve pain that may persist after the rash has cleared. When she visits her corneal specialist, he jokes, "Doesn't Natalie look good for 65?"
In fact, most shingles sufferers in Canada are over the age of 60; the lifetime risk of getting the disease is 15 to 20 per cent. But some doctors and epidemiologists believe that the chicken pox vaccine, licensed in Canada in 1999, may alter the dynamics of the disease. Prior to the introduction of the vaccine, about 90 per cent of Canadians were infected with varicella by age 12. Post-vaccine, outbreaks have been drastically reduced; between 2003 and 2009, there was a 70 per cent reduction in the number of children hospitalized for chicken pox. Strangely enough, this decline, says Dr. Allison McGeer, director of infection control at Toronto's Mount Sinai Hospital, may actually lead to an increase in the rate of shingles among an unfortunate group of young adults who had chicken pox before the rollout of the vaccine.
Here's why: according to studies conducted in the 1960s by the British GP and epidemiologist Robert Edgar Hope-Simpson, those who are repeatedly exposed to chicken pox - health care workers, say, and families with young children - are less prone to a reactivation of the virus. Greater exposure actually lessens the risk of shingles. It follows, McGeer says, that the immune systems of young adults who didn't get the varicella vaccine won't have that extra boosting that would help prevent shingles - the younger, vaccinated generation won't provide any exposure. So adults in their 20s and 30s have two strikes against them: they've had the virus, so it can be reactivated, and they haven't had the exposure that would heighten their immunity. "They are going to have a problem," concludes McGeer.
Though it's too early to know just how big the problem will be - not until January 2007 did all provinces and territories implement routine immunization programs for varicella - the U.S. experience is instructive. South of the border, the vaccine was licensed earlier, in 1995, and though the incidence of chicken pox has decreased dramatically, "reports are beginning to circulate that the frequency of shingles is now higher," according to Dr. Richard Whitley, president of the Infectious Diseases Society of America. Like McGeer, he believes "we are going to see cases of shingles in younger and younger people because there's less chicken pox in the population now."
There is a silver lining, however. "If these people get shingles when they're 50 instead of when they're 80," notes McGeer, "this might not be a bad thing." Unlike in Natalie's case, the disease is typically less severe with fewer complications in younger adults. Plus, a shingles vaccine called Zostavax was authorized in Canada in 2008. But so far it has only been approved (and shown to be effective) for adults over the age of 60, and it protects only half of those vaccinated.
McGeer points out that with the speed of medical discovery today, there may soon be a vaccine to help younger people with shingles. But Dr. David Fisman, associate professor of epidemiology at the Dalla Lana School of Public Health at the University of Toronto, wonders about the efficacy of all of this vaccinating. "When the [chicken pox] vaccine first came in, there was the question of whether we should adopt it, because while infection was common, a typical chicken pox case was mild," he says. The economic losses caused by parents missing work to care for sick children were taken into account but, "no one really thought to question whether natural chicken pox has a 'booster' effect."
Right now, the National Advisory Committee on Immunization in Canada is reviewing new evidence on the benefits of a two-dose schedule for the vaccine, and the new guidelines will be published in the fall. Theoretically, two doses for children rather than the currently recommended single dose would provide even better protection against the virus. However, as Fisman says, "We may have created a different disease epidemiology for which the only fix would be to vaccinate more." So even seemingly benign medical innovations can have unintended consequences, leading Fisman and others to wonder if, with shingles, an ounce of prevention does not, in fact, equal a pound of cure.
Maclean's August 23, 2010