IStock Photo 3397550 © Jaren Wicklund

It was once a rite of childhood—like your first sleepover or learning to ride a bike. Children could virtually count on spending one miserable week at home with chickenpox. The virus, varicella-zoster, causes an outbreak of itchy, fluid-filled blisters and is easily transmitted from contact with infected skin or particles contained in a cough or sneeze. Although extremely contagious, it often led to little more than a week’s worth of scratching and a few days of mild fever. But thanks to a vaccine introduced in the US in 1995, today’s youth will only hear about chickenpox from their parents.

While it might seem odd to mount a nationwide vaccination campaign for a relatively mild disease, in some cases chickenpox can be more serious. According to the Centers for Disease Control, one in 10 unvaccinated children who develop chickenpox end up with complications that warrant a doctor’s visit. Before the vaccine became widespread, there were 10,600 chickenpox-related hospitalizations each year and between 100 and 150 deaths. Ten years after the vaccine was introduced, a 2005 report in the New England Journal of Medicine found chickenpox-related deaths had effectively been halved, averaging about 66 a year.

Today, the odds a toddler in the US has received the vaccine are 1 in 1.11 (90%), about the same odds that they have access to safe drinking water (1 in 1.1 - 91%). The incidence of chickenpox has also been much reduced. As of 2006, only 1 in 6,180 US citizens will get the disease in any given year, making it more likely to either die of colorectal cancer (1 in 5,587) or visit the emergency room due to a jewelry-related accident (1 in 3,758).

In addition to health benefits, the vaccine cut down on missed school time for kids, lost work hours for parents, and, a report in the journal Pediatrics says, it slashed chickenpox-related hospital bills by $100 million each year.

But the vaccine isn’t perfect. The CDC estimates that up to one in 5 individuals who receive the vaccine still contract the illness, although it is usually a milder infection. What’s more, according to a 2007 study in the New England Journal of Medicine, vaccine-delivered immunity fades over time, making a second, “booster” shot necessary as compared to the reward of lifetime immunity conferred on people who have suffered through the actual disease. Many experts worry that people who don’t develop permanent immunity from the vaccine may catch the virus later in life, when dangerous complications are much more likely.

Another area of concern is what the vaccine means for shingles, a condition caused by the same varicella-zoster that brings on chicken pox. The virus never leaves the body, and late in life, when immune systems weaken, it can reemerge as herpes zoster, or shingles—painful blisters and rashes that can lead to permanent nerve damage. Most doctors believe children vaccinated against chickenpox will be saved from shingles. But many researchers also believe that being around children with chickenpox acted as a sort of “booster” shot for adult immune systems. They worry that parents who now won’t be re-exposed to the virus by their children will have cases of shingles that are especially severe. A shingles vaccine has been developed and is recommended for some people 60 and over; however, so far clinical trials have shown that it reduces the risk of shingles by only 51%.

Due to fears of about vaccine side effects—and possibly the risk of shingles they face themselves—many parents are now bringing their children to “ chickenpox parties” in the hope they will “catch” the virus while they are young and presumably have a better chance of having a milder case than they might as adults. This isn’t some New Age parenting approach—according to the National Network for Immunization Information, chickenpox parties occurred long before a vaccine existed. But the CDC, which stands by the safety and effectiveness of the vaccine, warns there is no way to predict which person will have severe reactions to chickenpox. They advise parents, “it is not worth taking this chance.”