Pox talk: the pros and cons of the varicella vaccine

Thanks to the varicella (chicken pox) vaccine, the oatmeal baths and admonitions to avoid scratching that were once childhood rites of passage could soon become distant memories for many families. But some parents still struggle with the notion of immunizing against an illness that, while miserable, is often mild. So what are the arguments for — and against — the chicken pox vaccine? We’ve taken our best shot at gathering the information you need to decide what’s best for your family.

Q. Most of us had chicken pox as kids without any long-term problems. Why is there a big push to vaccinate children now?
A. For starters, the vaccine wasn’t available when most of us were kids — it was introduced in Japan about 20 years ago, and North American scientists studied it for several more years before it was approved for use in Canada in 1998.

So what’s the rationale for vaccinating children?

Minimizing misery According to Joanne Langley, a paediatric infectious disease specialist at the IWK Health Centre in Halifax and spokesperson for the Canadian Paediatric Society, a garden variety case of chicken pox produces two to five days of flu-like symptoms, including fever and 50 to 300 exquisitely itchy bumps that, if scratched, may scar. These lesions can crop up in the mouth, ears, urinary tract and genitals. The vaccine prevents the infection entirely in 70 to 90 percent of vaccinated kids; those who nonetheless get chicken pox usually experience much milder symptoms. That also means mom and dad may lose fewer workdays — no small matter for many families.

Cutting complications Sure, 90 to 95 percent of kids get through chicken pox with no trouble — but five to 10 percent experience complications, the most common of which involves blisters becoming infected with bacteria. (In fact, though cases are very rare, chicken pox can increase by 40 to 60 times the risk of developing serious group A streptococcal infections, one of which is flesh-eating disease.) Approximately 0.2 to 1.5 percent of infected kids will develop problems grave enough to require hospitalization, such as severe pneumonia or encephalitis, a swelling of the brain. And there’s no way of predicting who’ll be affected, stresses Langley. “Most kids who are hospitalized are previously healthy kids.”

Thankfully, chicken-pox-related deaths are rare, but they do occur. According to Diane Kelsall, an assistant professor of family medicine at the University of Toronto, 53 children died of chicken-pox-related causes in the decade before the vaccine was introduced in Canada in 1998. The toll since stands at six (all of whom were unvaccinated).

Trimming transmission Breakthrough (post-vaccination) chicken pox isn’t as contagious as the natural infection. There’s also evidence that the shot cuts the chances that classmates and family members will come down with the illness.

Zapping zoster Up to 20 percent of elderly people who contracted chicken pox as children develop an agonizing condition called shingles or zoster. What happens is this: After the initial varicella infection, the virus lives on in your body, where the immune system normally holds it in check. However, waning immune function (triggered by pregnancy, medications or age) allows the virus to reactivate, inflaming nerves. “It is recognized that getting the weakened virus that’s in the vaccine is associated with a much lower risk of getting shingles later,” notes Simon Dobson, a clinical associate professor of paediatric infectious diseases at BC Children’s Hospital in Vancouver.

Q. How does the chicken pox vaccine work?
A. Ordinarily, when a child catches chicken pox, the immune system learns to produce proteins called antibodies, which neutralize the varicella virus. The body then stores away the memory of what the virus looks like and how to make weapons specifically designed for fighting it off. When we encounter the virus thereafter, the attack is repelled before it causes sickness, so we’re said to be immune. The varicella vaccine uses a weakened virus to provoke antibody production: It’s a bit like soldiers practising manoeuvres with blanks in lieu of live bullets.

Q. Does immunization pose any risks?
A. The majority of side effects are minor, Langley reassures. “About 20 percent of people have pain, redness and swelling at the site of the injection,” she explains. Sometime in the 10 to 14 days following the shot, 10 to 15 percent of kids develop a temperature. Up to five percent develop a sort of mild version of chicken pox, breaking out in a slight blistery rash near where the needle was given. Fever-related seizures (which are usually harmless, if scary) occur in less than 0.02 percent of immunized kids. While other serious events have been reported after vaccination, they’re so rare it’s impossible to tell whether they’re due to the vaccine.

Q. Can a child have an allergic reaction to the vaccine?
A. Allergy is less of a concern than with some other vaccines, since the virus is not grown in eggs, Kelsall explains. However, children with severe allergies to gelatin or neomycin shouldn’t get the vaccine.

Q. Are there other kids who shouldn’t get vaccinated?
A. If your child is taking immune-suppressing medications such as oral steroids or chemotherapy drugs, your doctor will likely recommend deferring the shot until treatment is over.

Q. At what age should children be vaccinated?
A. The National Advisory Committee on Immunization recommends immunizing all children who don’t have contraindications. Normally, the needle is given between 12 and 15 months (though a recent study suggests it’s slightly more effective at 15 months). Waiting longer isn’t recommended because toddlerhood is a prime time for picking up the virus. However, if your older child hasn’t contracted chicken pox, she can still be immunized. (In fact, vaccination may be particularly worthwhile for children who haven’t gotten the disease before age 10, since the likelihood of complications climbs with age.) Kids 12 and older need two doses, four to eight weeks apart.

Q. Is immunization more important for some children than others?
A. Yes. Children who have cystic fibrosis are less likely to cope with chicken- pox-related lung complications. Kids who take Aspirin (to manage certain heart conditions, for example) are especially vulnerable to severe varicella infection. Ditto for kids with close family members who run a similarly high risk, due to suppressed infection-fighting ability brought on by chemotherapy, certain cancers and other illnesses.

Q. Which provinces and territories cover the cost?
A. According to the Canadian Coalition for Immunization Awareness and Promotion, Quebec and the Yukon are the only jurisdictions that don’t cover the shot when it’s administered at 12 to 15 months. Coverage of other age groups is — ahem — spotty: Some provinces pony up if kids have health problems placing them at risk of complications from chicken pox; others have catch-up programs at school entry. To find out what the policy is in your province, call your doctor’s office or regional health unit. Or check the Canadian Paediatric Society’s online table at cps.ca/english/statements/id/pidnoteimmunization 2005.htm.

Q. Will the vaccine work after my child’s been exposed to chicken pox?
A. “Giving the vaccine within five days of contact might not prevent all disease,” says Dobson, but it will prevent severe cases and reduce the odds of serious infection and complications.

Q. Why do some parents opt against the chicken pox vaccine? And are those reasons valid?
A. Some parents believe that risk of complications outweighs that of disease. As outlined above, a large body of research indicates this fear is unfounded. However, some parents may prefer to gamble on the illness since the risk of serious complications is still relatively low.

Others are concerned that vaccine-conferred immunity could ebb, pushing infection into later life — when risk of severe illness and complications is much higher. That’s one reason Kim Westgate-Rodgers, of London, Ont., has chosen not to immunize her two younger children against chicken pox (older brother Brendan has had it), though she’s an ardent believer in other vaccines. “I think I’d rather have them go through the illness and know it’s done,” she says.

Is this misgiving warranted? True, the vaccine hasn’t yet been around for a lifetime, so experts are uncertain exactly how long it safeguards against disease. However, while scientists are still studying the question of whether (and if so, when) booster shots will be needed, research has established the immunization can confer protection for as long as 22 years.

Q. Should you intentionally expose your kids to chicken pox?
A. While catching chicken pox could be the only sure way to guarantee life-long immunity, keep in mind the known risks of the infection are greater than those of the shot. Dobson suggests thinking about it this way: “One reason some people are shy of vaccines is that they can’t bear the thought that if something bad happened, vaccination was something they’d done deliberately. In a way, taking a kid to a chicken pox party is the same.”

Resources
Canadian Paediatric Society
caringforkids.cps.ca/handouts/vaccination_and_your_child

National Network for Immunization Information (US)
immunizationinfo.org/vaccineinfo