Alberta health officials say vaccine problems could be partly to blame for two long-standing outbreaks of whooping cough in the province.
"In some cases the vaccine may be waning, so the protective effect may wear off just before kids get their Grade 9 booster," said Dr. Digby Horne, central Alberta's chief medical officer.
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"And in some cases there is vaccine failure as well," he said, noting that roughly one-third of cases are in people who have been immunized.
There have been roughly 900 confirmed cases of whooping cough around the province over the last two years.
In the central region, there have been 211 confirmed cases since the beginning of 2014 — most of them children.
It would be good to have a better vaccine and of course it would be better if everyone was immunized and kept up to date - Dr. Digby Horne, central Alberta's chief medical officer
But Horne says that outbreak is slowing down and could be declared over within the next few weeks.
Meanwhile, an outbreak continues in northern Alberta with 239 cases confirmed this year.
Whooping cough, also known as pertussis, is a bacterial infection that causes severe coughing that lasts for weeks.
It can lead to pneumonia, convulsions, brain damage and even death, according to Alberta Health Services. Infants six months of age and younger are at greatest risk for serious complications.
"It would be good to have a better vaccine and of course it would be better if everyone was immunized and kept up to date," said Horne.
But health officials say immunization is still the best protection against the infection.
They target pregnant women at 26 weeks or more, because that can protect newborn babies.
For other children, Alberta offers shots against pertussis as part of the routine immunization program.
- Calgary Zone: 33 cases in 2014. So far in 2015, 51 cases.
- Edmonton Zone: 101 cases in 2014. So far in 2015, 116 cases.
- Central Zone: 128 cases in 2014. So far in 2015, 83 cases.
- North Zone: 42 cases in 2014. So far in 2015, 239 cases.
- South Zone: 56 cases in 2014. So far in 2015, 53 cases.