Health
Why 'waning immunity' from COVID-19 vaccines isn't as bad as it sounds – CBC.ca
This is an excerpt from Second Opinion, a weekly roundup of health and medical science news emailed to subscribers every Saturday morning. If you haven’t subscribed yet, you can do that by clicking here.
Canadians concerned over waning immunity from COVID-19 vaccines, breakthrough infections and the need for booster shots in the general public could benefit from a dose of some important context, experts say.
Antibodies, your first line of defence against COVID-19 infection, do decline — and may even be doing so as you’re reading this — but that’s not unexpected.
While one aspect of your vaccine-induced immunity to COVID-19 is technically “waning” in the weeks and months after vaccination, that’s not necessarily a bad thing — because it’s not your immune system’s only form of protection against the virus.
“I don’t even like the term,” said University of Toronto immunologist Jennifer Gommerman. “And the reason I don’t like the term is that it implies that the immune response in its entirety is declining.”
It’s “entirely normal” for antibody levels to drop initially after vaccination and your immune response to the virus to become “contracted” over time, she said. But your body is also creating “highly efficient” memory B cells to fight off COVID-19 long term.
B cells work quickly to generate large quantities of antibodies in the weeks after vaccination, but they typically produce more effective antibodies as time goes on, helping sharpen the long-term response to a virus.
So while reports of waning immunity may sound concerning, that initial decrease in antibody levels may also be necessary in the fight against COVID-19, as it helps fine-tune the immune system’s plan of attack.
A new study published in the journal Science found “robust cellular immune memory” from B cells for at least six months after mRNA vaccination against all circulating strains of the virus — even the highly contagious delta variant.
The researchers found those memory cells, unlike the initial wave of antibodies, continue to learn how to fend off the virus months after vaccination and are actually getting better at it over time.
“That doesn’t sound like ‘waning’ to me,” Gommerman said. “There’s a natural contraction, but waning implies that something bad is happening.”
Breakthrough infections don’t tell the whole story
Reports of waning immunity and breakthrough infections have sporadically emerged across Canada in places like the Northwest Territories and New Brunswick, but lack important context and data on who is seriously affected and why.
The N.W.T. has been in the midst of a COVID-19 outbreak since mid-August that started in the Sahtu region before spreading to Yellowknife and its surrounding communities. It has infected 1,584 residents.
During that time, there have been 54 hospitalizations attributed to the outbreak, about 17 of which were among fully vaccinated people. A government spokesperson declined to comment on how many of the nine deaths in the territory were among those fully vaccinated.
WATCH | Concerns over waning immunity leads to expansion of boosters in N.W.T.:
![](https://thumbnails.cbc.ca/maven_legacy/thumbnails/129/567/mpx-pretape-NWT-covid.jpg?crop=1.777xh:h;*,*&downsize=510px:* 510w")
Northwest Territories Chief Public Health Officer Dr. Kami Kandola talks about the impact of the fourth wave and why the territory is offering COVID-19 booster shots to residents as young as 50. 2:58
In New Brunswick, where reports that one in five COVID-19 deaths occurred in people who were fully vaccinated made headlines this week, the data shows that while 17 fully vaccinated people have died, evidence of widespread waning immunity is lacking.
“New Brunswick has not identified confirmed evidence of waning immunity among COVID-19 cases,” a government spokesperson said in a statement.
In terms of national numbers, 94.7 per cent of all COVID-19 cases in Canada since Dec. 14 have been among those not fully vaccinated, as well as 95.8 per cent of hospitalizations and 94.3 per cent of deaths, according to the Public Health Agency of Canada (PHAC).
That means a total of 520 fully vaccinated Canadians have died of COVID-19 in the nearly 10 months since our vaccine rollout started, compared with 8,520 who were not considered fully vaccinated during that same time period.
“If we have 100 per cent or 95 per cent of the population vaccinated, almost all the cases that we see, including severe cases, will be in vaccinated people — just because most everyone’s vaccinated,” said Dr. Lynora Saxinger, an infectious diseases physician and associate professor at the University of Alberta.
“So that very rare outcome becomes the majority of the outcomes, and seeing an increasing number of cases in vaccinated people over time doesn’t actually mean that the vaccine works less well, necessarily.”
Underlying conditions key to breakthrough infections
PHAC says fully vaccinated Canadians who do get COVID-19 are also 79 per cent less likely to be hospitalized and 64 per cent less likely to die, backing up new Canadian data showing strong vaccine protection from infection, hospitalization and death.
But key information on the age, underlying health conditions or specific vaccine combination administered to those who were hospitalized or died from COVID-19 two weeks after their second shot is not available in Canada due to health privacy laws.
The recent death of former U.S. Secretary of State Colin Powell from COVID-19 sparked fresh debate about breakthrough infections and waning immunity. But less attention was paid to the fact he was at heightened risk due to a blood cancer called multiple myeloma.
Older, frailer Canadians living with comorbidities in congregate settings, such as long-term care facilities, are at increased risk of breakthrough infections because their antibody levels drop “much faster” than in the general population, said Gommerman.
A recent preprint study from the Toronto-based Lunenfeld-Tanenbaum Research Institute at Sinai Health analyzed 119 Ontario long-term care residents and 78 staff over four months, finding much lower levels of neutralizing antibodies in the elderly patients.
Gommerman also stresses there’s an important difference between infections and disease.
“We expect people to get infected — even healthy people to get infected — as antibody levels decline, because the only thing that can protect you against a breakthrough infection are antibodies,” she said.
“But we have to think about who we’re looking at, and what underlying comorbidities might be there in people who experienced breakthrough disease.”
Other immunocompromised groups, such as transplant patients, have shown declining protection from COVID-19 vaccines, as evidenced in the New England Journal of Medicine from researchers at the University Health Network (UHN) in Toronto.
WATCH | NACI recommends COVID-19 booster shots for long-term care residents:
![](https://thumbnails.cbc.ca/maven_legacy/thumbnails/798/695/covid-boosters-naci-birak-280921.jpg?crop=1.777xh:h;*,*&downsize=510px:* 510w")
Amid a global debate over COVID-19 vaccine boosters, the National Advisory Committee on Immunization is recommending third doses for Canada’s most vulnerable, especially seniors in long-term care homes. 1:58
“If you are a healthy person and you’ve been fully vaccinated, you don’t need to worry about getting severe COVID-19,” Gommerman said.
“If you are worried about getting infected with SARS-CoV-2, you should worry because you have people around you who are not vaccinated or who are under-immune.”
Boosters for general population ‘premature’ in Canada
New data from researchers at the Institute for Clinical Evaluative Sciences (ICES) in Toronto, which has not yet been peer-reviewed, found fully vaccinated people over 16 in Ontario were highly protected against both infection and severe COVID-19 after eight months.
ICES’s vaccine estimates, which have not yet been published, show that protection against symptomatic infection does drop — from 94 per cent to 81 per cent — but protection against severe outcomes remained high, at more than 90 per cent.
“The main takeaway is that we don’t need to do boosters at this time for the general population. We can hold off and wait and see — and when we start seeing the waning, then that’s when we should use the boosters,” said Dr. Jeff Kwong, an epidemiologist and senior scientist at ICES.
“It would be premature to do it at this time and not in our best interest, because we’re allowing other variants to emerge potentially if we let the pandemic spread uncontrolled in other parts of the world [where] they’re not vaccinated.”
WATCH | PHAC reviewing data supporting COVID booster shots in Canada:
![](https://thumbnails.cbc.ca/maven_legacy/thumbnails/614/3/tamboosters_1800kbps_1280x720_1962387523965.jpg?crop=1.777xh:h;*,*&downsize=510px:* 510w")
Chief Public Health Officer Dr. Theresa Tam says Canada’s Public Health Agency is reviewing the data supporting third doses of a COVID vaccine and will issue recommendations soon. 1:23
Saxinger said the vast majority of Canadians who get severely ill or hospitalized after full vaccination are the very elderly, the immunocompromised, transplant patients and people with certain types of cancers.
“That group of people, of course, they should get a third dose,” she said. “But even with a third dose, they still are going to remain vulnerable as long as we have circulating virus in the community.”
Health
Avian influenza spread: WHO gives public health warning as FDA calms food safety concerns – Food Ingredients First
23 April 2024 — The World Health Organization (WHO) has warned that the ongoing spread of avian influenza poses a “significant public health concern” and urged health authorities, especially in the US, to closely monitor infections in cows. However, the US FDA maintains that the virus is not currently a concern to consumer health and downplayed its impact on commercial milk production.
Earlier this month, the largest producer of fresh eggs in the US halted production at a Texas plant after bird flu was detected in its chickens. Cal-Maine Foods said that about 3.6% of its total flock was destroyed after the infection.
However, the virus, also known as H5N1, has now been found in at least 26 dairy herds across eight US states, marking the first time this strain of bird flu has been detected in cattle, according to officials.
At least 21 states have restricted cattle importations from states where the virus is known to have infected dairy cows.
The US Department of Agriculture’s Animal and Plant Health Inspection Service strongly recommends minimizing the movement of cattle, but has not issued federal quarantine orders.
Public health threat
The US Centers for Disease Control and Prevention (CDC) confirmed this month that a dairy worker in Texas, who reportedly had exposure to dairy cattle presumed to have had avian influenza, contracted the virus and is now recovering.
“This infection does not change the H5N1 bird flu human health risk assessment for the US general public, which CDC considers to be low,” the agency said in a press release, while acknowledging that people who come into more frequent contact with possibly infected birds or other mammals have a higher risk.
Meanwhile, WHO’s chief scientist, Dr. Jeremy Farrar, told reporters recently in Geneva, Switzerland, that H5N1 has had an “extremely high” mortality rate among the several hundred people known to have been infected with it to date.
US health officials have downplayed the impact of bird flu on food safety and industry production.However, no human-to-human H5N1 transmission has yet been recorded.
“H5N1 is an influenza infection, predominantly started in poultry and ducks and has spread effectively over the course of the last one or two years to become a global zoonotic — animal — pandemic,” said Farrar.
“The great concern, of course, is that in doing so and infecting ducks and chickens — but now increasingly mammals — the virus now evolves and develops the ability to infect humans.
“And then critically, the ability to go from human-to-human transmission.”
Concerns with cattle
US health officials have stressed that bird flu’s risk to the public is low, and the country’s food supply remains safe and stable.
“At this time, there continues to be no concern that this circumstance poses a risk to consumer health or that it affects the safety of the interstate commercial milk supply,” the FDA said in a statement.
According to officials, farmers are being urged to test cows that show symptoms of infection and separate them from the herd, where they usually recover within two weeks.
US producers are not permitted to sell milk from sick cows, while milk sold across state lines must be pasteurized or heat-treated to kill viruses, including influenza.
A dairy worker in Texas reportedly contracted the virus after exposure to cattle.
“We firmly believe that pasteurization provides a safe milk supply,” Tracey Forfa, director of the FDA’s Center for Veterinary Medicine, told a webinar audience last week.
However, WHO’s Farrar has urged further caution by public health authorities “because it [the virus] may evolve into transmitting in different ways.”
“Do the milking structures of cows create aerosols? Is it the environment which they’re living in? Is it the transport system that is spreading this around the country?” he said.
“This is a huge concern, and I think we have to…make sure that if H5N1 did come across to humans with human-to-human transmission that we were in a position to immediately respond with access equitably to vaccines, therapeutics and diagnostics.”
According to a new European Food Safety Authority report, outbreaks of avian influenza continue to spread in the EU and beyond.
By Joshua Poole
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York Region Public Health is reminding residents to keep up to date on their vaccinations as National Immunization Awareness Week begins.
The regional municipality said it is important to stay up to date on recommended vaccinations to ensure protection from contagious diseases. That includes updated COVID-19 vaccinations for vulnerable populations, recommended as part of a spring vaccination campaign.
“We know vaccines are safe and the best way to stay protected against vaccine-preventable disease,” the region said in a news release.
National Immunization Awareness Week runs from April 22 to 30, with this year’s theme being “Protect your future, get immunized.”
This spring, the region is still doing COVID-19 vaccinations. While walk-ins are no longer available as of April 2, you can book an appointment to visit a York Region clinic.
The spring COVID-19 vaccination campaign is aimed at more vulnerable groups who have received a COVID-19 vaccine before. Those include seniors, those living in seniors living facilities like long-term care homes, immunocompromised individuals and those in Indigenous households who are 55 or older. Public health also recommends the COVID-19 vaccine for those who have not yet received one.
York Region Public Health is also reminding residents of the need for other vaccines.
Measles cases have sprung up in Ontario and York Region recently. The region is recommending that people ensure they previously raised two valid doses of the measles vaccine. The region will also start providing measles vaccines April 29 for those overdue and for who do not have access to the vaccine through a health-care provider.
School-aged vaccinations are also available for free for children in junior kindergarten to Grade 12.
You can access immunization information at york.ca/immunziations or by contacting Access York at 1-877-464-9675.
“Vaccination helps protect everyone in our families, communities and schools,” the region said. “ By continuing to stay up to date on your immunizations, you help protect infants who are too young to be vaccinated and those not able to get vaccinated due to medical conditions.”
The World Health Organization (WHO) said the rising number of bird flu cases has raised “great concern” because it had an “extremely high” mortality rate among those who had been infected around the world.
The WHO’s data show that from 2003 through March 2024, a total of 889 worldwide human cases of H5N1 infection had been recorded in 23 countries, resulting in 463 deaths and a 52 percent mortality rate. The majority of deaths occurred in Southeast Asian countries and Egypt.
The most recent death was in Vietnam in late March, when a 21-year-old male without underlying conditions died of the infection after bird hunting. So far, cases in Europe and the United States have been mild.
Jeremy Farrar, chief scientist at the WHO, said recently that H5N1, predominantly started in poultry and ducks, “has spread effectively over the course of the last one or two years to become a global zoonotic — animal — pandemic”.
He said that the great concern is that the virus is increasingly infecting mammals and then develops the ability to infect humans. It would become critical if the virus develops the ability to “go from human-to-human transmission”, Farrar said.
In the past month, health officials have detected H5N1 in cows and goats from 29 dairy herds across eight states in the US, saying it is an alarming development because those livestock weren’t considered susceptible to H5N1.
The development worries health experts and officials because humans regularly come into contact with livestock on farms. In the US, there are only two recorded cases of human infection — one in 2022 and one in April this year in Texas. Both infected individuals worked in close proximity to livestock, but their symptoms were mild.
Wenqing Zhang, head of the WHO’s global influenza program, told the Daily Mail that “bird-to-cow, cow-to-cow and cow-to-bird transmission have also been registered during these current outbreaks, which suggest that the virus may have found other routes of transition than we previously understood”.
Zhang said that multiple herds of cow infections in the US states meant “a further step of the virus spillover to mammals”.
The virus has been found in raw milk, but the Texas Health Services department has said the cattle infections don’t present a concern for the commercial milk supply, as dairies are required to destroy milk from sick cows. In addition, pasteurization also kills the virus.
Darin Detwiler, a former food safety adviser to the Food and Drug Administration and the US Agriculture Department, said that Americans should avoid rare meat and runny eggs while the outbreak in cattle is going on to avoid the possibility of infection from those foods.
Nevertheless, both the WHO and the Centers for Disease Control and Prevention (CDC) said that the risk the virus poses to the public is still low. Currently no human-to-human infection has been detected.
On the potential HN51 public health risk, Farrar cautioned that vaccine development was not “where we need to be”.
According to a report by Barron’s, under the current plan by the US Health and Human Services Department, if there is an H5N1 pandemic, the government would be able to supply a few hundred thousand doses within weeks, then 135 million within about four months.
People would need two doses of the shot to be fully protected. That means the US government would be able to inoculate about 68 million people — 20 percent — of 330 million in case of an outbreak.
The situation is being closely watched by scientists and health officials. Some experts said that a high mortality rate might not necessarily hold true in the event the virus became contagious among people.
“We may not see the level of mortality that we’re really concerned about,” Seema Lakdawala, a virologist at Emory University, told The New York Times. “Preexisting immunity to seasonal flu strains will provide some protection from severe disease.”
Agencies contributed to this story.
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