Widespread vaccination has virtually eliminated chicken pox deaths in North America, particularly in children, a new study shows.
Research published Monday in the medical journal Pediatrics reveals that the annual number of deaths attributed to chicken pox in the U.S. has fallen to an average of 14 annually since the vaccine was approved in 1995. Prior to the vaccine, the average was 105 deaths annually.
"Chicken pox deaths are becoming a thing of the past," said Jane Seward, deputy director of the division of viral diseases at the U.S. Centers for Disease Control and Prevention in Atlanta.
Ms. Seward noted that deaths fell in all age groups, but the drop was sharpest in the pediatric population - 97 per cent, compared to 88 per cent in adults. There is also anecdotal evidence that hospitalizations and physician visits for treatment of chicken pox are down substantially.
There are no up-to-date Canadian data. However, according to the Public Health Agency of Canada, six children died between 2000 (when the chicken pox vaccine was introduced in Canada) and 2005. In the decade prior, there were six deaths a year on average.
Chicken pox is caused by varicella zoster virus. It is mainly a disease of childhood; an estimated 90 per cent of unvaccinated children in Canada will contract chicken pox by age 12. While it is generally benign, aside from bothersome itchy blotches and fever, in rare instances varicella can have serious complications like pneumonia, flesh-eating disease and stroke.
While relatively few adults contract chicken pox, they are far more likely to suffer life-threatening complications than children. In Canada, immigrants from tropical countries - where chicken pox is virtually non-existent - are at particular risk.
Ms. Seward said one of the most intriguing aspects of the new research is the drop in chicken pox deaths in adults and babies. While few adults have received the vaccine, and babies under 12 months are too young to receive the vaccine, widespread childhood immunization means children are far less likely to spread the disease to adults.
The researcher also noted that, between 1995 and 2005, children received only one dose of chicken pox vaccine. Since 2005, a two-dose schedule has been used, and incidence of the disease has fallen even more.
The chicken pox vaccine, sold under the brand name Varivax, is a product is Merck Frosst Canada. It is now a routine childhood vaccination in all 13 provinces and territories so the cost is covered by the state.
Children who contract chicken pox, even if they don't get terribly sick, are far more likely to contract shingles, a painful disease, as older adults. It is still unclear what impact vaccination will have on the incidence of shingles in the decades to come. There is a vaccine that protects against shingles called Zostavax; it is also a product of Merck Frosst.