Playing chicken with group A streptococcal infection
CMAJ 2000;163(3):321
The case for chickenpox vaccination has been boosted by a recent study showing that children who had contracted chickenpox had a dramatically increased risk of acquiring group A streptococcal (GAS) infection (Pediatrics 2000;105[5]:e60).
The project surveyed invasive GAS infection in Ontario over 5 years, identifying 205 children with the infection. Of the children who had GAS, 15% had had chickenpox in the previous month, representing a 58-fold increased risk of acquiring the infection. In addition, necrotizing fasciitis developed in 4% of the children. The researchers speculate that the GAS bacteria may enter the body when the skin barrier is broken down by chickenpox lesions. Alternatively, the varicella-zoster viral infection may create a predisposing immune aberration.
"The most compelling evidence for chickenpox vaccination is that the economic burden is so high," says Dr. Dele Davies, associate professor of microbiology, infectious diseases and pediatrics at the University of Calgary, and one of the lead researchers. There are more than 300 000 cases in Canada each year, costing millions of dollars. The cost of hospitalizing a patient is more than $7000. "It is not always as mild as people think," explains Davies.
The Canadian Paediatric Society recommends universal vaccination for children at 1 year of age. Varicella vaccine has been available in Canada since 1998; however, at $60 per dose it is the most expensive vaccine available. Another limitation is the need to store it at a temperature of –15°C degrees, unlike most vaccines, which can be kept refrigerated at 2°C to 8°C. (A new chickenpox vaccine that does not require freezing has recently been developed). "Those two things have prevented a wide uptake of the vaccine right away," says Davies. Varicella vaccination is funded by the provincial health plan only in Prince Edward Island, although some other provinces, such as Alberta and Ontario, are planning to introduce funded vaccination. In Alberta, it is available at private clinics.
Davies hopes that his work will help speed up the move to universal vaccination. "Chickenpox is the last preventable childhood illness in Canada, and the most common cause of preventable death. Why should we be content with that situation?" — Heather Kent, Vancouver
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