New Omicron Variants Combined With Waning Immunity For Many Canadians Lead To A Tricky Debate As Health Canada Looks Out For Concerning Trends
As the protection given by a third dose of COVID-19 vaccine begins to wane for many Canadians, the question is quickly rising of whether eligibility for a fourth shot should be expanded and if so, when.
Its a topic on which infectious disease experts are not in universal agreement.
Currently, a fourth dose of vaccine is only available across Ontario to those deemed at higher risk for severe COVID-19 outcomes.
But as new Omicron subvariants are emerging, some say its important that the public gain an immunity boost before the next wave, as research shows protection dips about six months after the first booster shot.
Were hitting a period where the bulk of people who have had two shots or more are in a period of waning immunity, said Todd Coleman, an epidemiologist at Wilfrid Laurier University. It would be prudent to offer and open up the fourth shot to the general population.
The protection against COVID-19 that vaccines offer declines after about six months, said Coleman.
Others, meanwhile, say the fourth dose is likely most helpful for immunosuppressed and older people, and that it may not provide enough benefit for the population at large to offer it to everyone at this point.
Second booster dose immunization programs for other high-risk groups and the general public may be needed in the future if data suggest concerning trends in COVID-19 pandemic, Health Canada told the Star in a statement.
How Are We Monitoring The Coronavirus Vaccines
Pfizer and Moderna have been monitoring immunity in people who were given their vaccines in the initial clinical trialsboth companies had reported strong overall efficacy at the six-month mark.
One thing researchers are monitoring in vaccine recipients is levels of antibodies, which are proteins produced by the bodys immune system when it detects harmful substances, and that are easily measured from blood samples. Antibodies are a really good marker for protection against infection, so we will be monitoring those levels for as long as we can measure them, says Akiko Iwasaki, PhD, a professor of immunobiology at Yale School of Medicine.
I tell my family, ‘It’s great that youre vaccinated… But even the vaccines dont have 100% guarantees, so… you want to keep weighing the risks,'” says Yale Medicine infectious diseases expert Jaimie Meyer, MD, MS
A report in The New England Journal of Medicine in April showed that 33 participants who had received the Moderna vaccine during the Phase I trial had a gradual decline in antibody protectionand, based on the slope, Iwasaki says, that is hopeful news. If antibodies are going down very quickly, you would expect that to last for a short time. The slow decline raises hopes that the mRNA vaccines will be protective for at least a year, if not longer, she says.
This is a reason why the CDC recommends vaccinations for people who have had a COVID-19 infection as well as for those who have not.
Pfizer Data Shows Positive Results For Ages 5 To 11 Ahead Of Fda Expert Panel Meeting
This data comes from a study of over 2,000 children who received 2 doses of either the Pfizer vaccine or a placebo a substance with no medication in it. Children in the study received one-third of the dose thats used for people ages 12 and older.
Compared to people ages 12 and older who received the Pfizer vaccine, side effects were similar for these younger children. Younger children generally had more redness and swelling at the injection site but less fever, headache, and tiredness.
Right now, the Pfizer vaccine can be given to people ages 12 and older. The Moderna and J& J vaccines can be given to adults ages 18 and older. If authorized, this would be the first COVID-19 vaccine available for children younger than 12 years old.
In early October, Pfizer asked the FDA to authorize their COVID-19 vaccine for this age group. An FDA expert panel is meeting this week to review these findings. A CDC expert panel is scheduled to meet next week. Both agencies need to sign off before the vaccine can be used for this age group.
What this means: A lower-dose version of the Pfizer vaccine appears to be safe and effective for children 5 to 11 years old.
What this doesnt mean: The vaccine is already available to be used in this age group. If appropriate, the FDA may authorize the vaccine in the coming days.
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What We Know So Far About Waning Vaccine Effectiveness
As tens of millions who are eligible in the United States consider signing up for a Covid-19 booster shot, a growing body of early global research shows that the vaccines authorized in the United States remain highly protective against the diseases worst outcomes over time, with some exceptions among older people and those with weakened immune systems.
But while the vaccines effectiveness against severe disease and hospitalization has mostly held steady, even through the summer surge of the highly transmissible Delta variant, a number of published studies show that their protection against infection, with or without symptoms, has fallen.
Public health experts say this decline does not mean that the vaccines are not working.
In fact, many studies show that the vaccines remain more than 50 percent effective at preventing infection, the level that all Covid vaccines had to meet or exceed to be back in 2020. But the significance of these declines in effectiveness and whether they suggest all adults should be eligible for a booster shot is still up for debate.
Effectiveness against symptomatic infection
Weeks since second dose
A study in England examined the vaccines effectiveness against the Delta variant over time. It found that the Pfizer-BioNTech vaccine is about 90 percent effective at preventing symptomatic infection two weeks after the second dose but drops to 70 percent effective after five months.
When Does It Start Working
The Pfizer vaccine is given in two doses scheduled three weeks apart. It’s not ideal but, according to the Centers for Disease Control and Prevention , the second dose may be given up to 6 weeks after the first dose, if necessary. You should not get the second dose early.
These doses are given as injections and offer full protection two weeks after the second dose, the CDC says. The data suggest that after the first dose, some immune response is present in about two weeks.
A CDC report that tracked almost 4,000 healthcare personnel, first responders, and other frontline workers under real-world conditions found that the mRNA vaccines were 80% effective at least 14 days following the first dose and 90% effective at least two weeks after the second dose.
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Vaccine Protection And Transmission
COVID-19 vaccines are crucial tools in the pandemic response and protect against severe disease and death. Vaccines provide at least some protection from infection and transmission, but not as much as the protection they provide against serious illness and death. More evidence is needed to determine exactly how well they stop infection and transmission.
After being vaccinated, individuals should continue taking simple precautions, such as physical distancing, wearing a mask, keeping rooms well ventilated, avoiding crowds, cleaning hands, and coughing into a bent elbow or tissue. Get tested if you are sick, even if youve been vaccinated. Check local advice where you live and work. Do it all!
What Takes So Long
Despite differences in mRNA vaccines like Pfizer and viral vector vaccines like AstraZeneca, both take similar amounts of time to generate antibody responses. After a single dose of AstraZeneca, antibodies can be detected after 14 days and further increase over the next two weeks.
But why does it take time for these responses to develop? When researchers track the antibody response to the first dose of vaccine, they find it takes at least ten days for the immune system to start making antibodies that can recognise SARS-CoV-2s spike protein .
In contrast, the second dose activates the immune system much more quickly. Within a week of dose two, your antibody levels increase by more than ten times, providing much stronger and longer-lasting protection from infection.
So the first dose of a COVID vaccine gets your immune response going, but the second dose is essential to ensure immunity is strong, consistent from person to person, and longer-lasting.
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Commonly Reported Adverse Events
The most commonly reported adverse events with COVID-19 vaccines are expected vaccine side effects, such as headache, fatigue, muscle and joint pain, fever and chills and pain at the site of injection. The occurrence of these adverse events is consistent with what is already known about the vaccines from clinical trials.
Phase Two And Three Clinical Trials Vaccine And Placebo
The efficacy of the Pfizer vaccine was tested in about 44,000 participants aged 16 years and over where COVID-19 was already circulating in communities. About half of these participants were randomised to receive the vaccine and the other half received a saline placebo.
The trial looked at how many people got COVID-19 symptoms after they were vaccinated compared to how many got COVID-19 after getting the placebo.
Participants had two doses of the vaccine or placebo, getting their second dose within 19 to 42 days after their first dose. They were then closely monitored and evaluated for at least 2 months after their second dose.
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Vaccine Rollout Takes Shaky First Steps
Vaccine rollout for children under 5 wont look like the ones for older kids and adults, according to Dr. Ashish Jha, the White House COVID response coordinator.
Instead of mass vaccination sites, other more familiar locations like doctors offices, health clinics, pharmacies, and childrens hospitals will administer most of the jabs because thats what parents prefer, Jha wrote on Twitter.
We want to build a response and an availability system that is responsive to parents needs and desires, he said, adding that well see more and more vaccines and appointments open up as sites receive their first orders, which were shipped last week.
But eager caregivers are already running into issues, an early sign that they say reveals poor planning on the governments end.
Lauren Thompson told us she called her local health department in Virginia last week to find out whether her county will have vaccines for kids under 5 as soon as they become available. She was told they were waiting to see if there was a demand for the shots before ordering any. Thompsons pediatrician then told her their office was interested in the vaccine but wont have it when its first available.
Im grateful that I have access to PTO, as well as a car to be able to make the trip there, she said. Why was there no solid distribution plan?? Why is everything so inequitable?
You can find nearby providers that have vaccines in stock on vaccines.gov.
Vaccination Can Help Prevent Complications From Covid
The CDC recently published three different reports about potential COVID-19 vaccine benefits. Data about how well the vaccines work against the Delta variant is somewhat limited, so these reports aim to help fill this gap.
The first report used data collected between early April and mid-July 2021 in 13 different U.S. jurisdictions. This was a large study that analyzed about 600,000 cases, almost 38,000 hospitalizations, and over 6,000 deaths related to COVID-19.
The report found that fully vaccinated people compared to people not fully vaccinated against COVID-19 are about 5 times less likely to be infected with COVID-19 and more than 10 times less likely to be hospitalized or pass away due to complications from COVID-19. This report includes data from the Delta variant.
What this means: Being fully vaccinated against COVID-19 helps lower your risk against infection and COVID-19-related complications.
What this doesnt mean: COVID-19 vaccines are the only way to lower your virus-related risks. If you arent fully vaccinated, you can still help protect yourself in other ways.
To read more about this study, click or tap here.
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What Did The Researchers Do
Like all coronaviruses, SARS-CoV-2 the virus that causes COVID-19 has spike proteins on its surface that give it the ability to latch onto and infect cells. The Omicron variant of SARS-CoV-2 and its most common subvariant have spike proteins that are better at doing this than the original virus.
Vaccines against SARS-CoV-2 prompt the immune system to make neutralizing antibodies Y-shaped proteins that bind to the virus and prevent it from infecting cells. Researchers wanted to know whether the vaccines available today stimulate enough antibodies to protect people from BA.2.
Researchers tested antibodies from the blood of 24 people after vaccination and booster doses of the Pfizer-BioNTech vaccine. They also looked at antibodies from eight people who had recovered from COVID-19, seven of whom had been vaccinated.
Participants who had a two-dose vaccination and received a booster shot had a high number of antibodies that could recognize BA.2 and BA.1. That number was even higher than the number of antibodies that could recognize the original SARS-CoV-2 after a two-dose vaccination.
People who received only the primary two-dose vaccination had far fewer neutralizing antibodies against BA.2 20 times lower than the number of antibodies that recognized the original SARS-CoV-2.
Duration Of Effectiveness Of Vaccines Against Sars
- Contributed equallyAffiliationsInternational Vaccine Access Center, Department of International Health, John Hopkins Bloomberg School of Public Health, Baltimore, MA, USA
- Rafael AraosAffiliationsInstituto de Ciencias e Innovacion en Medicina, Facultad de Medicina, Clinica Alemana Universidad del Desarrollo, Santiago, ChileAdvanced Centre for Chronic Diseases, Santiago, Chile
- National Institute for Communicable Diseases, Division of the National Health Laboratory Service, Johannesburg, South AfricaSchool of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
- Amit HuppertAffiliationsThe Gertner Institute for Epidemiology and Health Policy Research, Sheba Medical Centre, Tel Aviv University, Tel Aviv, Israel
- Contributed equallyAffiliationsInternational Vaccine Access Center, Department of International Health, John Hopkins Bloomberg School of Public Health, Baltimore, MA, USA
- Contributed equally
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What This Means For You
More research needs to be done, but it’s become clear that COVID-19 vaccines will need to be given more than just once. It’s likely that boosters and annual vaccineswhether the existing shots, or other therapies yet to be developedwill be needed throughout your life.
Like most vaccines, the COVID-19 vaccines work in more than one way to prevent infection. The first involves the production of antibodies.
Your body uses antibodies to fight off infection, but not as easily when it has never seen a novel, or new, virus. Because COVID-19 was a new virus, human bodies had not developed an antibody defense for it. The vaccines help it to achieve that.
The second way the vaccines work is to help the body develop responses in what are called memory B cells and T cells. These are immune cells that store information for future reference.
However, immunity does wane. Your individual response and other factors contribute to this loss of protection. Like human memory, cellular memory is short. Booster shots help to “remind” it to respond to a virus or other pathogen. Here’s how each of the current vaccines work.
How Long Does It Take For The Body To Build Antibodies From The Time Of Infection With The Coronavirus Disease
People develop antibodies when their body’s immune system responds to an infection. These antibodies can be found in the blood of people previously infected whether or not they had signs or symptoms of illness. Note: It can take 12 weeks after the first symptoms appear for antibodies to develop in the body. Since it often takes about a week for symptoms to appear after getting infected with SARS-CoV-2, antibodies could develop about 2-3 weeks after infection. This means serology tests may not detect current SARS-CoV-2 infections and should not be used to diagnose current COVID-19.
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How Long Are Covid
- Experts dont know yet how long COVID-19 vaccines will be effective.
- Studies of two of the most prominent COVID-19 vaccines suggest they remain effective for at least six months.
- The CEO of one vaccine maker said immunity may start to fade within a year.
One of the most pressing questions about COVID-19 vaccines is how long they can provide protection.
It may be decades, or a matter of months the data necessary to figure that out is accumulating every day. Pfizers CEO said this week that after a full regimen of doses immunity will probably start to fade within a year. According to the WHO, its simply too early to know the exact duration of COVID-19 vaccines because both the disease and the science deployed against it arent yet fully understood.
Some early evidence is promising. The viruses that caused MERS and SARS are closely related to the virus behind COVID-19, and acquired immunity to both of those diseases has proved relatively durable.
In terms of COVID-19-specific research, Pfizer and BioNTech said earlier this month that their vaccine remains effective for at least half a year after the second dose, and a study of Modernas version reflected a similar duration. Immunization efforts will have to play out further before we can know more for certain.
For more context, here are links to further reading from the World Economic Forum’s Strategic Intelligence platform: