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Between one-quarter and one-half of new immigrants and refugees are susceptible to measles, mumps and rubella — infectious diseases that have been virtually eliminated in Canada through childhood vaccination, a new study reveals.

The research warns that the steady influx of unvaccinated newcomers could trigger outbreaks of these potentially deadly diseases. In fact, recent outbreaks of mumps and rubella originated in immigrant communities.

The best ways to avoid these problems is to create “catch-up” immunization programs for newcomers, according to the research team, led by Christina Greenaway of the division of infectious diseases at Sir Mortimer B. Davis Jewish General Hospital in Montreal.

The study, published in this week's edition of the medical journal Annals of Internal Medicine, notes that vaccinations are not verified or updated for adult immigrants or refugees to Canada.

This situation exists despite the fact that 70 per cent of newcomers to Canada come from countries where rates of routine immunization are poor, the researchers report.

Since 1996, the United States has required that new immigrants have updated vaccinations as part of mandatory medical testing prior to arrival. But it is believed that large gaps remain because of incomplete record-keeping and a lack of mechanisms to verify vaccination status.

To conduct the study, Dr. Greenaway and her team tested 1,480 immigrants and refugees who arrived in Montreal between October, 2002, and December, 2004.

Rather than rely on the recall of participants, researchers actually tested their blood for antibodies to measles, mumps and rubella. The presence of antibodies means that a person has either been exposed to the disease or been vaccinated — but either way they are no longer susceptible to infection.

Overall, 36 per cent of immigrants and refugees in the study were susceptible to one or more of the infectious diseases studied. However, levels of susceptibility varied widely based on area of origin.

Newcomers from East Asia, South Asia and Latin America were the least likely to have adequate vaccine coverage. Women were significantly less likely to have been vaccinated than men.

In Canada, most children are routinely vaccinated against nine common infectious agents: diphtheria, tetanus, pertussis, measles, mumps, rubella, polio, Haemophilus influenza B and hepatitis B.

It is also recommended that children receive five other vaccines — meningococcal infection, pneumococcal infection, chicken pox, adolescent pertussis (whooping cough) and influenza. However, not all of these shots are provided free across Canada. While it is widely assumed that virtually every child in Canada receives basic childhood vaccines, a study released last year revealed that one in three toddlers had not received their recommended vaccinations by age 2.

Large numbers of young children were falling through the cracks despite an average of 19 doctors' visits in their first two years of life and the fact that basic childhood vaccines are provided free.

Researchers at the Institute for Clinical Evaluative Sciences in Toronto found that the failings were due principally to a lack of continuity of care — notably, a lack of a family physician or pediatrician, and the absence of electronic health records to track immunizations.

That study found that low rates of immunization were a problem especially in immigrant and refugee children, reinforcing the call for targeted vaccination programs.