The idea of waning immunity has picked up steam in recent weeks, with some countries using it to justify rolling out third-dose COVID-19 vaccine boosters to their populations. But immunologists say the concept has been largely misunderstood.
While antibodies — proteins created after infection or vaccination that help prevent future invasions from the pathogen — do level off over time, experts say that’s supposed to happen.
And it doesn’t mean we’re not protected against COVID-19.
Jennifer Gommerman, an immunologist with the University of Toronto, said the term “waning immunity” has given people a false understanding of how the immune system works.
“Waning has this connotation that something’s wrong, and there isn’t,” she said. “It’s very normal for the immune system to mount a response where a ton of antibodies are made and lots of immune cells expand. And for the moment, that kind of takes over.
“But it has to contract, otherwise you wouldn’t have room for subsequent immune responses.”
Antibody levels ramp up in the “primary response” phase after vaccination or infection, “when your immune system is charged up and ready to attack,” said Steven Kerfoot, an associate professor of immunology at Western University in London, Ont.
Memory of pathogen remains
They then decrease from that “emergency phase,” he said. But the memory of the pathogen and the body’s ability to respond to it remain.
Kerfoot said B-cells, which make the antibodies, and T-cells, which limit the virus’s ability to cause serious damage, continue to work together to stave off severe disease long after a vaccine is administered. While T-cells can’t recognize the virus directly, they determine which cells are infected and kill them off quickly.
Recent studies have suggested the T-cell response is still robust several months following a COVID-19 vaccination.
“You might get a minor infection … [but] all of those cells are still there, which is why we’re still seeing very stable effectiveness when it comes to preventing severe disease,” Kerfoot said.
A pre-print study released this week by Public Health England suggested that protection against hospitalization and death remains much higher than protection against infection, even among older adults.
So the concept of waning immunity depends on whether you’re measuring protection against infection or against severe disease, Kerfoot said.
Ontario reported 43 hospitalized breakthrough cases among the fully vaccinated on Friday, compared with 256 unvaccinated hospitalized infections. There were 795 total new cases in the province that day, 582 among those who weren’t fully vaccinated or had an unknown vaccination status.
British Columbia, meanwhile, saw 53 fully vaccinated COVID-19 patients hospitalized over the last two weeks, compared with 318 unvaccinated patients.
“You’ll hear people say that vaccines aren’t designed to protect infection, they’re designed to prevent severe disease,” Kerfoot said. “I wouldn’t say necessarily it’s the vaccine that’s designed to do one or another … that’s just how the immune system works.”
Moderna, Pfizer back need for booster
Moderna released real-world data this week suggesting its vaccine was 96 per cent effective at preventing hospitalization, even amid the more transmissible delta variant, and 87 per cent effective at preventing infection — down from 94 per cent efficacy seen in clinical trials last year.
Moderna CEO Stéphane Bancel said that dip “illustrates the impact of waning immunity and supports the need for a booster to maintain high levels of protection.”
Pfizer-BioNTech has argued the same with its own data, and an advisory panel to the U.S.-based Food and Drug Administration voted Friday to endorse third doses for those aged 65 and older or at high risk for severe disease.
However, the panel rejected boosters for the general population, saying the pharmaceutical company had provided little safety data on extra jabs.
The University of Toronto’s Gommerman said the efficacy data presented by Moderna doesn’t signal the need for a third dose.
“The fact it protects 87 per cent against infection, that’s incredible,” she said. “Most vaccines can’t achieve that.”
Bancel said Moderna’s research, which has yet to be peer reviewed, suggested a booster dose could also extend the duration of the immune response by re-upping neutralizing antibody levels.
Looking beyond the antibody response
But Dr. Sumon Chakrabarti, an infectious physician in Mississauga, Ont., said looking solely at the antibody response is misleading and could be falsely used as justification for an infinite number of boosters.
Israel, which has opened third doses for its citizens, recently talked about administering fourth doses in the near future.
“This idea of waning immunity is being exploited, and it’s really concerning to see,” Chakrabarti said. “There’s this idea that antibodies mean immunity, and that’s true … but the background level of immunity, the durable T-cell stuff, hasn’t been stressed enough.”
While some experts maintain that boosters for the general population are premature, they agree some individuals would benefit from a third jab.
The National Advisory Committee on Immunization has recommended boosters for the immunocompromised, who don’t mount a robust immune response from a two-dose series.
Other experts have argued that residents of long-term care homes, who were prioritized when the rollout began last December, may also soon need a third dose. The English study suggests immunity could be waning in older groups but not much — if at all — among those under age 65.
Chakrabarti said a decrease in protection among older populations could be due more to “overlapping factors,” including their generally weaker immune systems and congregate-living situations for those in long-term care.
Immune cells live for years within bone marrow
“These are people at the highest risk of hospitalization,” he said. “Could [the length of time that’s passed following their doses] be playing a role? Yeah, maybe.”
While we still don’t know the duration of the immune response to COVID-19 vaccination, Gommerman said immune cells typically continue to live within bone marrow and make small amounts of antibodies for “decades.”
“And they can be quickly mobilized if they encounter a pathogen,” she said.
Pfizer-BioNTech booster shot '95 per cent effective' – The National
Trial results have found that having a third or “booster” dose of the Pfizer-BioNTech Covid-19 vaccine is more than 95 per cent effective at preventing disease.
The clinical trial findings, released by the two companies that developed the shot, are described as the first efficacy results from a “randomised, controlled Covid-19 vaccine booster trial”.
There were more than 10,000 participants in the trial, all of whom had completed an initial two-dose programme with the vaccine.
Half the participants then received a third dose of the vaccine, and half were given a placebo, with the third dose given an average of 11 months after the second.
Researchers recorded whether participants subsequently developed symptomatic Covid-19 at least seven days after the booster was given, with individuals followed up for an average of 2.5 months.
In the boosted group there were just five Covid-19 cases, while in the non-boosted group 109 cases were recorded, which gives an efficacy – or effectiveness at preventing disease – of 95.6 per cent.
Prof David Taylor, professor emeritus of pharmaceutical and public health policy at University College London, said the results indicated “having a booster is an extremely sensible idea” for people in at-risk groups.
“The message to everybody, including if you’re 50 or 60 or over, is having a booster dose after six months or longer is extremely sensible,” he said.
In a statement, Ugur Sahin, the chief executive and co-founder of BioNTech, said the results added to the “body of evidence” that the vaccine protected “a broad population of people from this virus and its variants”.
“Based on these findings we believe that, in addition to broad global access to vaccines for everyone, booster vaccinations could play an important role in sustaining pandemic containment and a return to normalcy,” he said.
Pfizer and BioNTech said detailed analysis of the results indicated that efficacy of a booster did not vary with age, sex, race, ethnicity, or any other serious medical conditions a person has.
The companies plan to share the results with regulators, including the Food and Drug Administration in the US and the European Medicines Agency.
A booster programme using the Pfizer-BioNTech vaccine that began in Israel in July has been credited with helping the country overcome its fourth wave of Covid-19 infections.
Infection rates fell faster in over-80s, who were given boosters first, than in other age groups, indicating that the third doses were improving immunity, which may have waned over time after the second dose.
Other countries are also launching booster programmes, including the UK, which began a programme last month focused on over-50s and other vulnerable groups.
In August, Abu Dhabi mandated a third dose of the Sinopharm vaccine for people who had previously received the Chinese-developed shot.
More recently, at the beginning of this month, the UAE authorised booster shots of the Pfizer-BioNTech and Russian-developed Sputnik vaccines for over 60s and members of other vulnerable groups, with the third dose to be given at least six months after the second.
Prof Taylor said it was unclear at the moment whether people would need to have Covid-19 vaccination boosters indefinitely.
“For the next few years, it does look like especially the older population will need top-up immunisation. Whether that will be twice-yearly or yearly we don’t know,” he said.
Updated: October 22nd 2021, 3:20 AM
Toronto police officers who ignore COVID-19 vaccinate mandate policy will be put on unpaid leave – CBC.ca
Toronto police officers who aren’t fully vaccinated or haven’t disclosed their COVID-19 vaccination status by Nov. 30 will be put on indefinite unpaid leave, the service says.
Any such member, uniformed or not, will not be allowed to enter buildings until they comply with the mandatory vaccine and disclosure policy.
Those members will also not be eligible for promotions to supervisory or management positions, the service said in a news release Thursday.
“Vaccination against COVID-19 protects the health and safety of each of our members, our workplaces and the public we serve,” said Chief James Ramer.
Consistent communication needed for kids COVID-19 vaccine rollout: experts – Delta-Optimist
Kelly Grindrod remembers the confusion pharmacists felt last spring as Canada’s COVID-19 vaccine policy changed rapidly throughout the rollout, sometimes with little warning.
Shifting eligibility requirements differed across the country, booking sites were harder to navigate in some regions, and one vaccine product came to be seen as inferior to the rest, infuriating the public and vaccinators alike.
Grindrod, an associate professor at the University of Waterloo and the pharmacy lead for Waterloo Region’s vaccine rollout, hopes provinces learned lessons from Canada’s first vaccination campaign for adults.
And if a COVID-19 vaccine is soon approved for children, she said a kid’s rollout needs consistent and clear messaging.
“Communication was a real challenge,” Grindrod recalled. “(Policy) would be announced nationally and everybody on the ground had to scramble because we were all hearing it at the same time.
“Immediately the phones would go crazy in pharmacies because people were trying to make sense of it…. We need a bit more lead-in, a bit more clarity, so (vaccinators) have answers before people start calling.”
Pfizer-BioNTech asked Health Canada to authorize its COVID-19 vaccine for kids aged five-to-11 this week. The regulator is reviewing data before making a decision.
Prime Minister Justin Trudeau said Thursday that Pfizer is ready to ship millions of child doses in the event of authorization, while Public Services and Procurement Minister Anita Anand added that Canada has already procured syringes and other supplies needed to speed up the rollout.
In the United States,an advisory group with the Food and Drug Administration, which received an approval request from Pfizer earlier this month, is scheduled to meet next week. The Centers for Disease Control and Prevention is then set to discuss authorization in early November.
Grindrod said U.S. regulators, which sometimes stream meetings online, have shown “more transparency around the (decision-making) process.”
Health Canada and the National Advisory Committee on Immunization supply “fairly comprehensive” documents after they’ve made decisions, she said, but vaccinators could use a heads up “to facilitate planning.”
Logistics of the kids rollout — where children get a vaccine, how they book appointments and whether certain kids will be prioritized — are still to be determined. Ontario said Tuesday it was open to running mass vaccine clinics at schools after school hours.
Omar Khan, an immunology and infectious disease expert with the University of Toronto, said school clinics are a great way to reach more kids. Pharmacies and family doctors can also help, but proper scheduling — which includes flexibility around parents’ work hours — is needed to ensure half-empty vaccine vials aren’t tossed at the end of the day.
“Anything that reduces accessibility barriers will help distribute (vaccines) to the queue of people waiting to get vaccinated across multiple sites,” he said.
Most logistics can be ironed out once supply is determined, Grindrod said.
Pfizer’s pediatric vaccine involves a different formulation, but Grindrod said some pharmacists have asked whether they must wait for kid-specific shipments or if a diluted adult dose could serve if supply was scarce. She urged clear information as soon as possible.
Messaging around the kids vaccine in general has to be handled with more care, she said,starting with whatever NACI and Health Canada recommend after reviewing its safety and efficacy.
“We need very careful communication … because we haven’t seen the data,” she said. “There are questions that need to be answered very clearly — what is the risk of COVID to kids at the point at which vaccines become available? What are the known side effects we expect to see based on data from trials?
“And then separately, what are the unknowns?”
Science communicator Samantha Yammine noted the difficulty in maintaining consistent vaccine advice when the science on COVID-19 evolved quickly throughout the pandemic.
Policies introduced midway through the adult rollout, such as NACI’s recommendation against using AstraZeneca for second doses, seemed to contradict earlier advice. But public health messaging constantly adapts to new data, she said.
While communication was confusing at times, the country still vaccinated nearly 82 per cent of its eligible population to date.
Since parents are likely more concerned about vaccinating children than getting the jab themselves, fears should be addressed honestly and parents made to feel part of the plan, Yammine said.
That includes equipping parents with child-friendly information they may need to field youngsters’ questions about the vaccine, she added.
And kids’ comprehension level shouldn’t be underestimated.
“I’m advising people to acknowledge how great a job kids have done,” Yammine said. “Wearing masks, understanding why they have to play with friends outside, it’s been really hard on kids.
“But they’ve shown us they can be involved and they can understand complex things.”
This report by The Canadian Press was first published Oct. 21, 2021.
Melissa Couto Zuber, The Canadian Press
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