Whooping cough cases skyrocket in Canada. What’s happening? – National

Whooping cough cases continue to rise in many provinces, but doctors and health officials say there may be multiple factors behind the surge as children return to schools.

The bacterial infection, also known as whooping cough, usually appears seven to 10 days after infection, and its symptoms usually 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 from two to eight weeks, or even up to 10 weeks, according to the U.S. Centers for Disease Control and Prevention.

The biggest increase was in Quebec, where more than 11,000 cases were reported last week, surpassing pre-pandemic levels. New Brunswick declared an outbreak on Aug. 22, with 141 cases — exceeding the five-year average.

According to PHAC, the provinces of Quebec, Prince Edward Island, New Brunswick and Newfoundland and Labrador have recorded case numbers that exceed the peak years preceding the COVID-19 pandemic, with Alberta, Ontario, Nunavut and British Columbia reporting outbreaks this year. An average of 3,000 cases of whooping cough were reported per year between 2015 and 2019, and that number has already been exceeded by the more than 12,000 reported this year so far, PHAC said, citing media reports.

Dr. Isaac Bogoch, an infectious disease specialist at Toronto General Hospital, said the availability of vaccinations may be a factor.

According to Bogoch, there are certain groups of people who may not have access to vaccinations from their GP or public health clinic; others may not want to get vaccinated, and still others may not get a dose of the vaccine due to disruptions in healthcare caused by COVID-19.

The World Health Organization said in a 2021 report that 3.5 million children worldwide had not received their first dose of vaccine.

However, the reason for the sharp increase in disease incidence cannot be solely the lack of vaccinations.

Bogoch and other experts say several factors may be contributing to this.

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

He adds that doctors should be on the lookout for people with a prolonged or severe cough because while it may not necessarily be whooping cough, early detection, testing and confirmation of infection can help ensure appropriate treatment and prevent the spread of the disease.

While doctors emphasize 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.

The formula has also evolved over time.

“So the first thing is to make sure that children going back to school are up to date on their vaccinations,” Banerji said.

Routine vaccinations should be given at ages two, four, six and 12 to 23 months — usually given at 18 months — with a booster dose between ages four and six and another at ages 14 to 16. Last week, 34 per cent of cases in Quebec were in people aged 10 to 14.

Dr. Earl Rubin, a pediatric infectious disease specialist in Montreal, told Global News that infants are among the most susceptible to the disease, which is why pregnant women in their third trimester should get a booster dose of the vaccine.

“That way, the mothers will be vaccinated, they will develop antibodies or protection against whooping cough, those antibodies will cross the placenta and hopefully protect the newborn at least until they start the vaccination series at two months of age,” Rubin told Global News.

He added that adults should generally consider taking a booster dose because prolonged, severe coughing is known to cause rib fractures and chest muscle pain.

The whooping cough vaccine has undergone some changes over the years, which Rubin notes could have contributed to the longer duration of immunity.

The combined whole-cell diphtheria-tetanus-pertussis vaccine was used before 1997, when it was replaced by a new acellular pertussis vaccine that has seen a steady decline in the rate of disease, PHAC said. The rate of disease refers to the number of new cases.

Rubin told Global News that switching from the whole-cell vaccine to the acellular one has resulted in higher vaccination rates because the newer formulation causes fewer adverse reactions.

The whole-cell vaccine used before 1997 sometimes caused severe neurological irritability and “difficult-to-control seizures.” The British Green Paper on Information for Physicians noted that a reduction in febrile seizures was observed in Canada after this change.

Rubin noted, however, that while this change had positive “balance of risk benefits,” the acellular vaccine did not provide as long-lasting immunity as the previous version, which later resulted in the need for more booster doses.

The question of the extent to which the newer vaccine formulation might be less durable has been frequently debated in medical journals, with some noting differences in data results depending on the vaccine manufacturer and specific formulations.

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

“This idea is partly challenged by newer studies that suggest the DTaP vaccine provides long-lasting, although imperfect, protection.”

A peer-reviewed article published in the Canadian Medical Association Journal in 2006 also noted that acellular vaccines may trigger the need for more booster doses to maintain immunity.

“Inactivated fractionated pertussis vaccines, such as acellular vaccines, have been introduced into routine immunization programs because of their improved adverse event profile and comparable immunogenicity in tests with previously used whole-cell pertussis vaccines,” the authors noted.

“However, our results suggest that in the short term, some acellular vaccines may not provide full protection against pertussis 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 responses). As a result, children need additional doses to achieve adequate levels of immunity. On the other hand, whole-cell vaccines tend to induce higher levels of cellular immunity.”

However, medical experts emphasize that the most important thing is to get vaccinated with a vaccine available and approved where you live and to get vaccinated regularly when necessary.

Banerji said the combination of close contact and expired vaccines in many people is likely to cause a further rise in cases.

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

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

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