Immigrant more likely vaccinated (study)
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|Thu, 05-22-2008 - 1:22pm|
Immigrant children more likely to get all their vaccinations: study
TORONTO — A study designed to see if children of immigrants were as likely to be vaccinated as children whose parents were born in Canada found a difference between the two groups.
But to the surprise of the scientists who conducted the study, vaccination rates were higher among the children of new Canadians. The researchers, from the Institute for Clinical Evaluative Sciences in Toronto, had thought rates might be lower in this group, especially among children of refugees.
Lead author Dr. Astrid Guttmann said it was "very heartening" to see that children of immigrants are at least as likely to be vaccinated as children whose parents were born in Canada.
"(But) everybody could be doing a little better," said Guttmann, a scientist with the institute and a pediatrician practising at Toronto's Hospital for Sick Children.
That's because the study found that just 66.5 per cent of all children in Ontario had received all recommended shots by two years of age. Among two-year-olds whose parents were immigrants, the rate was 69 per cent. Among children of refugees, 66.6 per cent were fully vaccinated at age two.
Those numbers aren't ideal, Guttmann suggested.
"In the world of immunization coverage there's some notion that as you start to get towards 60 per cent coverage in a population, that's when you really lose your herd immunity," she said.
Herd immunity refers to a phenomenon where enough people in a population are immune to a bacteria or a virus - either because they've got natural immunity or because they were vaccinated against it - that it no longer routinely circulates within that population.
There are some caveats to the picture painted by the study, published in the May issue of the journal Ambulatory Pediatrics. For one thing, it's not a recent picture. In fact, it's a decade old.
The researchers looked for evidence of vaccinations administered to more than 98,000 babies born in urban Ontario hospitals between July 1, 1997 and June 30, 1998. (Children born in rural settings were excluded because in some rural areas public health nurses and nurse practitioners give childhood vaccinations. So those shots wouldn't be captured by the doctors' billing records.)
They also only looked at Ontario children. As such, they cannot say what the situation was in other parts of the country.
"My research can't say that. But if you do a little digging around, you'll find that you can't find coverage estimates from many provinces," Guttmann said.
"And those that you do, it's a pretty mixed picture. And certainly the national statistics don't look terrific."
The most recent national estimates of vaccination rates for Canada published are based on a survey conducted in 2004 for the Public Health Agency of Canada. Every two years the agency conducts a telephone survey asking parents which vaccinations their children have received.
The 2004 survey suggests that 94 per cent of children have had a single dose of measles, mumps and rubella vaccine by their second birthday. Coverage for the recommended second dose of measles vaccine was 79 per cent.
Rates were lower for diphtheria (78 per cent), pertussis (74 per cent), tetanus (73 per cent), polio (89 per cent) and Hemophilus influenza type b, or Hib (73 per cent).
But when the survey results were analyzed to see if children had received their shots at the times recommended by the National Advisory Committee on Immunization, only 61 per cent had received all their immunizations within the advised timeframe, the report showed.
Still, the interim director of immunization policy at the Public Health Agency said that while the rates are lower than national targets, they've been improving.
"Our coverage surveys indicate that we have a good coverage of immunization," Mahnaz FarhangMehr said from Ottawa.
"It's not at the level that the national goals and recommendation is recommending yet. But we're getting there. For some antigens we are at 95 per cent, 94 per cent and we're getting very, very close to where we should be."