Updated at 10:12 PM 30 Jan 2008
By Jen Skerritt http://www.winnipegfreepress.com/breakingnews/story/4113937p-4709728c.html
Children who have their routine vaccinations delayed by two months or more cut their risk of asthma by half, a University of Manitoba researcher has found.
Anita Kozyrskyj, an asthma researcher in the U of M faculty of pharmacy, studied the immunization and health records of 14,000 children born in Manitoba in 1995.
Kozyrskyj found nearly 14 per cent of the children who received their first shot of diphtheria, pertussis, tetanus vaccine at two months of age developed asthma — compared with only 5.9 per cent of children who were vaccinated more than four months after the scheduled date.
Manitoba recommends vaccinating children at two months, four months, six months and 18 months of age for diphtheria, pertussis (whooping cough) and tetanus (DPT).
The DPT causes an allergic reaction and Kozyrskyj said researchers are speculating whether children's immune systems are better able to handle the vaccine's side effects when they're older. The pertussis vaccine used in Manitoba before 1997 caused fever in some children, and some studies have linked fever in early childhood to a greater risk of developing asthma.
The study's findings are going to be published in the U.S. Journal of Allergy and Clinical Immunology within the next few weeks.
"We're thinking that maybe if you delay this allergic response until a bit later, the child's immune system is more developed and maybe you're not seeing this effect," Kozyrskyj said.
The findings come as little surprise to parents who have spoken out against the risks of vaccinating infants at an early age.
The prevalence of childhood disorders like asthma and auto-immune disorders like autism has increased over the last few decades, leaving many parents wondering whether childhood vaccinations may be contributing to the rise.
"They're barely out of the protection of the womb before we're sticking vaccines in them," said Irene Gergus, a Winnipeg mom whose son Andrew lost his ability to speak shortly after receiving his fourth DPT shot at 18 months in 1993.
"I'm not against vaccination I just think they're too young to be receiving (them)."
Kozyrskyj is the first researcher to study the effect between asthma and vaccines, but said she doesn't believe the findings will spur a change the province's vaccination schedule. She said Japan recommended children under 10 months not be vaccinated between 1975 and 1988, and the country saw a spike in the number of childhood cases of whooping cough.
Kozyrskyj said she is "pro-vaccination" and noted the safety and efficacy of vaccines has been studied for years.
"It's not an alarm bell," she said. "We have many years of research on these vaccines and I would say the benefits, by far, outweigh the risks."
Of the 14,000 immunization records Kozyrskyj studied, 11,531 children received at least four doses of DPT.
Overall, nearly 12 per cent of the children who received at least four doses of DPT had asthma. The majority of children who had asthma lived in urban areas and were predominantly male.
Kozyrskyj said researchers did not compare the risk of asthma among children who did not receive any vaccinations, saying only about 100 children in the province did not receive DPT — a number that would not be statistically significant.