Whooping cough outbreak continues in Alberta's South Zone; declining vaccination rates seen as big driver

LETHBRIDGE -

This year alone, 304 Albertans have contracted pertussis, better known as whooping cough.

And 279 of those cases are in the province's South Zone.

Declining vaccination rates in the South Zone are seen as a big driver behind the outbreak.

"What we have seen in general across Canada and in Alberta, and in particular in places in southern Alberta, are those vaccine rates have dropped over the last 10 years," said Craig Jenne, professor of microbiology, immunology and infectious diseases at the University of Calgary.

In 2022, 70.7 per cent of children across Alberta were vaccinated against whooping cough.

But in the South Zone, just 58.1 per cent of children were vaccinated.

Lethbridge–West had the highest vaccination rate of an area in the South Zone, at 78.8 per cent.

Lethbridge–North and Lethbridge–South also ranked highly, coming in at 75.4 per cent and 67.1 per cent.

The County of Forty Mile had the lowest rate of vaccination in the zone with just 21.9 per cent.

These numbers fall well short of what's needed for herd immunity.

"The benchmark for herd immunity is really dependent on how infectious a given disease is. So, unfortunately, whooping cough is one of the more infectious viruses that we know of. And as a result, the benchmarks for herd immunity are somewhere above 90 per cent, actually very close to 95 per cent," Jenne said.

Low vaccination rates follow a trend over a decade in the making.

In 2008, 76.2 per cent of children in the South Zone were vaccinated against whooping cough.

Alberta-wide numbers also dropped, from 77.5 per cent in 2008 to 70.7 per cent in 2022.

"We've seen immunizations falling really for more than a decade. There is a fair bit of pushback from some groups on vaccines in general. Despite the fact we have decades of experience with this particular vaccine and we know its efficacy," Jenne said.

The reported cases are also believed to be less than the actual number of cases.

According to Alberta Health Services, "Public health is unable to identify linkages between most of the recent cases, indicating there is likely more disease circulating in communities that is not being reported."

So far, no one has died as a result of the outbreak.

Young children are at the greatest risk of health complications.

The worst outbreak of whooping cough was in 2017 when 461 cases were reported.