Whooping cough cases are increasing in Canada. What’s going on? – National

Whooping cough cases continue to rise in several provinces, but as children return to school, doctors and health care professionals say multiple factors could be behind the spike.

The bacterial infection, also known as whooping cough, typically develops seven to 10 days after exposure, and symptoms typically begin with a mild fever, runny nose and cough. The Public Health Agency of Canada notes that this can lead to coughing fits that can last two to eight weeks, or even up to 10 weeks, according to the U.S. Centers for Disease Control and Prevention.

Quebec sees the biggest jump, surpassing pre-pandemic levels with more than 11,000 cases last week, while New Brunswick an outbreak declared on August 22 with 141 cases, which exceeds the five-year average.

According to Dr. Isaac Bogoch, an infectious disease specialist at Toronto General Hospital, access to vaccination could be a factor.

Bogoch said there are groups of people who do not have access to vaccinations through a primary care physician or public health clinic. Others may choose not to get vaccinated. There are also people who have missed out on vaccinations due to health care disruptions caused by COVID-19.

The World Health Organization reported in a 2021 report that 3.5 million children worldwide missed their first dose of the vaccine.

But it is not just a lack of vaccination that is causing the increase.

Bogoch and other experts say there are a number of possible factors at play.

“Some of it could be related to the natural history of this particular infection, where there seems to be more of this infection every five or six years,” he said. “Some of it could be related to lower vaccination rates. Some of it could be related to declining vaccination over time.”

He adds that doctors should be alert to people with a prolonged or severe cough. While it may not be whooping cough, catching it early, getting tested and confirming the infection can help ensure it is treated appropriately and doesn’t spread.

While doctors stress that the vaccine “works quite well,” Dr. Anna Banerji, a pediatric infectious disease specialist in Toronto, told Global News that immunity can wane over time.

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The formulation has also evolved over time.

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What you need to know now that whooping cough cases are on the rise

“The first thing we need to do is make sure that children who are going back to school have their vaccinations up to date,” Banerji said.

Routine immunizations should be given at ages two, four, six and 12 to 23 months — usually given at 18 months — with a booster dose between four and six years and another at 14 to 16. As of last week, 34 percent of cases in Quebec were among 10- to 14-year-olds.

Dr. Earl Rubin, a pediatric infectious disease specialist in Montreal, told Global News that babies are most susceptible to the disease, so it’s wise for pregnant women to get a booster shot in the third trimester.

“That way the mothers get vaccinated, they build up an antibody or protection against whooping cough, that antibody crosses the placenta and hopefully protects the newborn until the vaccination series starts at two months of age,” Rubin told Global News.

He added that adults in general should consider getting a booster vaccination, as prolonged, severe coughing has been known to cause rib fractures and chest pain.

The whooping cough vaccine has undergone some changes over the years, which Rubin says may have affected long-term immunity.

The combined diphtheria-tetanus-whole cell-pertussis vaccine was used before 1997when a new acellular pertussis vaccine replaced it, showing a steady decline in the incidence of cases, PHAC says. Incident rate refers to the number of new cases.

Rubin told Global News that switching from a whole-cell vaccine to an acellular vaccine led to higher vaccination rates because there were fewer side effects with the newer formulation.

The whole-cell vaccine used before 1997 sometimes led to severe neurological irritability and “seizures that were difficult to control.” The Green Book of the United Kingdom of information for physicians noted that Canada saw a decrease in febrile seizures after the change.

However, Rubin noted that while the change had a positive “risk-balance benefit,” the acellular vaccine did not provide as long-lasting immunity as the previous version, leading to the need for more boosters later.

The question of whether the newer vaccine formulation might be less effective has also been widely discussed in medical journals, with some noting that the data showed varying outcomes depending on the vaccine manufacturer and the specific formulation.

“There are a number of hypotheses as to why this previously well-controlled disease is now re-emerging. It has been suggested that the less effective long-term protection (which wanes after 5-10 years) of DTaP has allowed epidemic cycles to re-establish,” noted an article in the journal Nature in September 2020.

“This is partly challenged by more recent studies claiming that DTaP provides long-lasting, albeit imperfect, protection.”

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NB is experiencing an outbreak of whooping cough

A peer-reviewed article in the Canadian Medical Association Journal in 2006 also noted that the acellular vaccines may raise the need to explore more boosters to maintain immunity.

“Inactivated fractionated pertussis vaccines such as acellular vaccines were introduced into routine vaccination programs because of their improved adverse event profile and comparable immunogenicity when tested with previously used whole-cell pertussis vaccines,” the authors of the article noted.

“However, our results suggest that some acellular vaccines may not provide sufficient protection against pertussis in the short term in infants and children under 5 years of age.

“This may be a consequence of the type of immunity generated by these vaccines (i.e., higher levels of humoral immunity or Th2-like responses). As a result, children require additional doses to achieve adequate levels of immunity. Whole-cell vaccines, on the other hand, tend to induce higher levels of cell-mediated immunity.”

However, medical experts stress that it is still most important to get vaccinated with the vaccine that is available and approved in your area, and to keep up to date with the latest developments as necessary.

The combination of close contact and outdated vaccines is likely to lead to a rise in cases, Banerji said.

“Now that children are going back to school and some children are not yet fully vaccinated, I expect an increase,” Banerji said.

“We’ve already had huge numbers, four times the normal whooping cough numbers that we normally see in Canada and really around the world, but I think that could increase as kids go back to school.”

— with files from Global News’ Saba Aziz and The Canadian Press