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Exposure to SARS-CoV-2 vaccination and infection may provide more durable immunity: Canadian study

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A study published in the Canadian Medical Association Journal (CMAJ) on Monday points to a significant change in the proportion of the Canadian population with SARS-CoV-2 antibodies over the first two and a half years of the pandemic and the probability that exposure to both vaccination and infection provides the most durable immunity.

The study, conducted by the British Columbia Centre for Disease Control (BCCDC) and involving almost 14,000 people, provides a clear view of the changing antibody landscape during the pandemic, and its findings hold implications for pandemic risk assessment and response, according to the authors.

During the pandemic, there was a change from virtually all pediatric and adult participants being immunologically naïve and susceptible to SARS-CoV-2 to almost all having been immunologically primed through vaccination or infection, or both.

By August 2022, most children and adults younger than 60 living in the lower mainland region of British Columbia, the location of the study participants, had acquired evidence of both SARS-CoV-2 vaccination and infection.

In the first year of the pandemic, most participants were immunologically naïve, or susceptible to the virus. “Thereafter, age-based vaccine roll-out dramatically changed the immunoepidemiological landscape such that, by September 2021, more than 80% of the study population had antibody evidence of immunological priming, while more than 85% remained uninfected,” the authors wrote.

Exposure to vaccination and infection “likely provides stronger, broader, and more durable hybrid immunity than either exposure alone, especially against severe outcomes,” the researchers added.

The findings related to the change in proportions of immunologically-naïve and immunologically-primed populations holds significant implications for pandemic risk assessment and response, the team observed.

“That is because primed individuals are expected to have swifter immune memory responses to reduce the risk, especially of severe outcomes, from novel viruses like SARS-CoV-2,” Dr. Danuta Skowronski, principal investigator and lead author of the study, said in an email. “Our serosurvey shows we are now much better poised to achieve [a reduced risk of severe outcomes] compared to the start of the COVID-19 pandemic.”

Older adults remain the most susceptible to severe outcomes. This population “remains most consistent with immunization goals to prevent serious morbidity and preserve health care capacity as the 2022-23 respiratory virus season begins,” the authors wrote.

Consequently, they suggested, older adults should be prioritized for vaccination.

The BCCDC had launched a SARS-CoV-2 baseline serosurvey in March 2020. “Baseline assessment was followed by additional serosurveys that spanned the time from mRNA vaccine availability in mid-December 2020 through seven pandemic waves associated with multiple variants of concern to August 2022,” the study authors wrote.

Eight cross-sectional serosurveys were conducted between March 2020 and August 2022, chronicling the evolution of pediatric and adult seroprevalence.

Participants were split into several age groups: 0-4; 5-9; 10-19; 20-29; 30-39; 40-49; 50-59; 60-69; 70-79; and 80 years or older. The team excluded individuals seeking SARS-CoV-2 antibody testing and residents of long-term care, assisted-living, and correctional facilities because of different pretest likelihood of positivity.

The first two serosurveys sampled 100 sera per age group; subsequent surveys sampled 200 per age group. The researchers obtained residual sera from the outpatient laboratory network LifeLabs and used at least three commercially available chemiluminescent immunoassays that target either the spike or nucleocapsid proteins for SARS-CoV-2. From this, they analyzed the antibody landscape and estimated seroprevalence in the population due to vaccination, infection, or both.

“By January 2021, we estimated that any seroprevalence remained less than 5%, increasing with vaccine rollout to 56% by May-June 2021, 83% by September-October 2021, and 95% by March 2022,” the authors wrote.

Infection-induced seroprevalence was low throughout September and October 2021, but increased with the emergence of a series of Omicron waves by March 2022 to 42% and by July and August 2022 to 61%.

Additionally, by August 2022, “[70% to 80%] of children younger than 20 years and [60% to 70%] of adults aged [20 to 59] years had been infected, but fewer than half of adults aged 60 years and older had been infected,” they continued.

The research team has plans to conduct further studies. “We plan further serosurveys among children, young adults, and most notably seniors to inform evolution in vaccine and infection-induced seroprevalence as relevant to ongoing risk assessment,” Skowronski said.

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Canada to donate up to 200,000 vaccine doses to combat mpox outbreaks in Africa

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The Canadian government says it will donate up to 200,000 vaccine doses to fight the mpox outbreak in Congo and other African countries.

It says the donated doses of Imvamune will come from Canada’s existing supply and will not affect the country’s preparedness for mpox cases in this country.

Minister of Health Mark Holland says the donation “will help to protect those in the most affected regions of Africa and will help prevent further spread of the virus.”

Dr. Madhukar Pai, Canada research chair in epidemiology and global health, says although the donation is welcome, it is a very small portion of the estimated 10 million vaccine doses needed to control the outbreak.

Vaccine donations from wealthier countries have only recently started arriving in Africa, almost a month after the World Health Organization declared the mpox outbreak a public health emergency of international concern.

A few days after the declaration in August, Global Affairs Canada announced a contribution of $1 million for mpox surveillance, diagnostic tools, research and community awareness in Africa.

On Thursday, the Africa Centres for Disease Control and Prevention said mpox is still on the rise and that testing rates are “insufficient” across the continent.

Jason Kindrachuk, Canada research chair in emerging viruses at the University of Manitoba, said donating vaccines, in addition to supporting surveillance and diagnostic tests, is “massively important.”

But Kindrachuk, who has worked on the ground in Congo during the epidemic, also said that the international response to the mpox outbreak is “better late than never (but) better never late.”

“It would have been fantastic for us globally to not be in this position by having provided doses a much, much longer time prior than when we are,” he said, noting that the outbreak of clade I mpox in Congo started in early 2023.

Clade II mpox, endemic in regions of West Africa, came to the world’s attention even earlier — in 2022 — as that strain of virus spread to other countries, including Canada.

Two doses are recommended for mpox vaccination, so the donation may only benefit 100,000 people, Pai said.

Pai questioned whether Canada is contributing enough, as the federal government hasn’t said what percentage of its mpox vaccine stockpile it is donating.

“Small donations are simply not going to help end this crisis. We need to show greater solidarity and support,” he said in an email.

“That is the biggest lesson from the COVID-19 pandemic — our collective safety is tied with that of other nations.”

This report by The Canadian Press was first published Sept. 13, 2024.

Canadian Press health coverage receives support through a partnership with the Canadian Medical Association. CP is solely responsible for this content.

The Canadian Press. All rights reserved.

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How many Nova Scotians are on the doctor wait-list? Number hit 160,000 in June

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HALIFAX – The Nova Scotia government says it could be months before it reveals how many people are on the wait-list for a family doctor.

The head of the province’s health authority told reporters Wednesday that the government won’t release updated data until the 160,000 people who were on the wait-list in June are contacted to verify whether they still need primary care.

Karen Oldfield said Nova Scotia Health is working on validating the primary care wait-list data before posting new numbers, and that work may take a matter of months. The most recent public wait-list figures are from June 1, when 160,234 people, or about 16 per cent of the population, were on it.

“It’s going to take time to make 160,000 calls,” Oldfield said. “We are not talking weeks, we are talking months.”

The interim CEO and president of Nova Scotia Health said people on the list are being asked where they live, whether they still need a family doctor, and to give an update on their health.

A spokesperson with the province’s Health Department says the government and its health authority are “working hard” to turn the wait-list registry into a useful tool, adding that the data will be shared once it is validated.

Nova Scotia’s NDP are calling on Premier Tim Houston to immediately release statistics on how many people are looking for a family doctor. On Tuesday, the NDP introduced a bill that would require the health minister to make the number public every month.

“It is unacceptable for the list to be more than three months out of date,” NDP Leader Claudia Chender said Tuesday.

Chender said releasing this data regularly is vital so Nova Scotians can track the government’s progress on its main 2021 campaign promise: fixing health care.

The number of people in need of a family doctor has more than doubled between the 2021 summer election campaign and June 2024. Since September 2021 about 300 doctors have been added to the provincial health system, the Health Department said.

“We’ll know if Tim Houston is keeping his 2021 election promise to fix health care when Nova Scotians are attached to primary care,” Chender said.

This report by The Canadian Press was first published Sept. 11, 2024.

The Canadian Press. All rights reserved.

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Newfoundland and Labrador monitoring rise in whooping cough cases: medical officer

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ST. JOHN’S, N.L. – Newfoundland and Labrador‘s chief medical officer is monitoring the rise of whooping cough infections across the province as cases of the highly contagious disease continue to grow across Canada.

Dr. Janice Fitzgerald says that so far this year, the province has recorded 230 confirmed cases of the vaccine-preventable respiratory tract infection, also known as pertussis.

Late last month, Quebec reported more than 11,000 cases during the same time period, while Ontario counted 470 cases, well above the five-year average of 98. In Quebec, the majority of patients are between the ages of 10 and 14.

Meanwhile, New Brunswick has declared a whooping cough outbreak across the province. A total of 141 cases were reported by last month, exceeding the five-year average of 34.

The disease can lead to severe complications among vulnerable populations including infants, who are at the highest risk of suffering from complications like pneumonia and seizures. Symptoms may start with a runny nose, mild fever and cough, then progress to severe coughing accompanied by a distinctive “whooping” sound during inhalation.

“The public, especially pregnant people and those in close contact with infants, are encouraged to be aware of symptoms related to pertussis and to ensure vaccinations are up to date,” Newfoundland and Labrador’s Health Department said in a statement.

Whooping cough can be treated with antibiotics, but vaccination is the most effective way to control the spread of the disease. As a result, the province has expanded immunization efforts this school year. While booster doses are already offered in Grade 9, the vaccine is now being offered to Grade 8 students as well.

Public health officials say whooping cough is a cyclical disease that increases every two to five or six years.

Meanwhile, New Brunswick’s acting chief medical officer of health expects the current case count to get worse before tapering off.

A rise in whooping cough cases has also been reported in the United States and elsewhere. The Pan American Health Organization issued an alert in July encouraging countries to ramp up their surveillance and vaccination coverage.

This report by The Canadian Press was first published Sept. 10, 2024.

The Canadian Press. All rights reserved.

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