Two shots are better than one to ward off chickenpox, the Canadian Paediatric Society said Tuesday as it recommended a new regimen for protecting the population from the highly contagious disease.
There's evidence that without a second dose of vaccine, some children will lose immunity as they get older and they might come down with chickenpox as adults, the organization said in a position statement.
"It's being brought in now because we have good surveillance and monitoring of our vaccine programs and we are keeping up to date also with things that are going on in the world," the principal author of the statement, Marina Salvadori, said in an interview from London, Ont.
"It's becoming obvious that one dose is unlikely to give lifetime protection, and is unlikely to prevent all outbreaks of chickenpox."
The statement puts the society in step with the National Advisory Committee on Immunization, which recommended a two-dose schedule for varicella vaccination a year ago.
The American Academy of Pediatrics called for a two-step immunization process in the United States in 2007.
Dr. Salvadori said the Canadian Paediatric Society now recommends that youngsters get the first dose between 12 and 18 months, and the second dose sometime between the ages of four and six.
Children who got only one dose as tots should get another one if they've never had chickenpox, and teenagers who have never had the disease should get two shots, at least four weeks apart, the statement said.
Dr. Salvadori said some, but not all, provinces provide public funding for a second dose, and the position statement is urging all provinces and territories to cover both shots.
Ontario launched a two-dose schedule last month, she noted.
The primary intent of the position statement is to direct individual doctors on the best practice of care, Dr. Salvadori.
"But we know that when we make a position statement, it sort of becomes the Canadian standard, and it puts a bit of pressure on provinces to publicly fund it," she said.
"So what we're really hoping is the provinces all pick this up, and it becomes introduced in the next year or two in all Canadian provinces for all Canadian children."
She also wanted to reassure parents who might think their kids are getting too many shots to protect against various ailments.
"There's always been a very careful weighing of risk and the benefit of the vaccine, and vaccines overwhelmingly show tremendous benefit to children," she said.
With technology and refinement, scientists have been able to reduce the number of antigens, or proteins, in the vaccine, so kids are getting less of an immune challenge than youngsters who got shots in the late 1970s and early 1980s, she explained.
"The vaccines that we give ... use only a tiny fraction of your immune system, and they protect you against serious diseases that cause serious illness, and can even cause death."
The main side-effect of the shot might be a "bit of a red sore arm, and you can get a very mild fever."
Chickenpox deaths are extremely rare, but before a vaccine was available, there were about 5,000 hospitalizations a year in Canada due to the disease, which is characterized by red spots that develop into fluid-filled blisters. In addition, there can be fever, headache, a dry cough and irritability.
After a chickenpox vaccine was introduced to Canada more than a decade ago, hospitalizations fell by up to 84 per cent in some provinces, Dr. Salvadori said.
She noted there were 115 deaths in 1995 in the United States attributed to chickenpox, compared to 16 deaths in 2003 after the vaccine was introduced.
Getting chickenpox is one of the primary ways that people can get group A strep infections or flesh-eating disease, Dr. Salvadori said.
Adults who get chickenpox have a higher death rate from the disease than kids, and are more likely to get pneumonia, the society noted.
The painful disease shingles is a reactivation of the varicella virus in adults who have previously had chickenpox.
CPS represents nearly 3,000 pediatricians and other child health professionals across Canada.
The Canadian Press