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What do I need to know about this year's flu shot? – CBC.ca

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Experts say it’s almost time to roll up your sleeve for the annual flu shot. 

But this year, some pharmacists say people have questions about the influenza vaccine rollout, which will coincide with the rollout of COVID-19 vaccines that target Omicron strains — also known as bivalent vaccines.

Ashley Davidson, a pharmacist and associate owner of Shoppers Drug Mart in St. Albert, Alta., has fielded a lot of questions.

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“So many people are asking about flu shots and I think a lot of that conversation comes around how do they time their vaccines and what does that look like?” she told Dr. Brian Goldman, host of CBC’s podcast The Dose

Here’s what experts have to say about this year’s flu vaccines. 

What do we know about the upcoming flu season?

The number of flu cases this year could look a little different than what we’ve seen over the last few years.

“What has changed in the last two years is we had historical lows throughout the pandemic and we’ve now been in the time of uncertainty about when is it going to come back, what is it going to look like,” said Dr. Robyn Harrison, vice-chair of the National Advisory Committee on Immunization (NACI) and infectious disease specialist, on Wednesday during a webinar on seasonal influenza.

An example of what could come is Australia’s recent flu season, which happens before Canada’s because it is in the southern hemisphere.

The country recently had its worst season in years, with data from Australia’s Department of Health and Aged Care showing influenza infections were higher than the five-year average and infections notably spiked, then dropped, earlier than usual. 

Canadians also haven’t had much exposure to flu over the last couple of years because of mask mandates and other public health measures introduced during the pandemic, Davidson said.

“One thing that stands out to me this year is that we won’t have masks in schools. So that is going to increase the potential exposure for flu virus for children as well,” she said. 

According to experts, influenza is a serious illness. Up until 2019, it is estimated that there are on average 12,000 hospital stays in Canada due to influenza every year, and about 3,500 deaths each year are caused by the flu, Harrison said.

Influenza is very contagious and spreads by respiratory droplets which cause an infection. Symptoms can vary but commonly include fever, sore throat, runny nose, cough, fatigue and muscle aches.

Who is eligible for a flu shot?

Experts say it’s important to get a flu shot each year as vaccine-induced immunity does wane over time. 

There are three types of influenza vaccines approved in Canada, according to NACI:

  • Inactivated influenza vaccine
  • Recombinant influenza vaccines
  • Live attenuated influenza vaccine

Anyone six months of age or older who does not have a known negative reaction to the vaccine should get a flu shot every year. 

“The reason why children under six months of age are not included in that is because we know that they don’t mount a good immune response to influenza vaccines,” said Dr. Jesse Papenburg, a pediatric infectious disease and medical microbiology specialist, during Wednesday’s webinar. He is also the chair of the NACI influenza working group. 

A health-care worker prepares a flu shot in Calgary. According to experts, it’s important to get a flu shot each year as vaccine-induced immunity does wane over time. (Leah Hennel)

He said the suggested flu shot schedule for children nine and older and adults is one dose of the influenza vaccine at the beginning of flu season. 

For kids aged six months to eight years who have yet to receive a flu shot, NACI recommends two doses given at least four weeks apart. 

Who shouldn’t get a flu shot?

Papenburg said NACI recommendations for those who shouldn’t get any of the flu shots include:

  • People who have had an anaphylactic reaction to any of the vaccine’s components, except for eggs.
  • People who have developed Guillain-Barré syndrome (GBS) within six weeks of a previous flu vaccine (unless another cause has been found).
  • Infants under six months of age.

NACI’s recommendations on who shouldn’t get the live attenuated influenza vaccine can be found here

When should I get a flu shot?

Davidson recommends that people get the influenza vaccine as soon as it’s available.

Canada’s flu season typically lasts from mid-October to April or early May, Davidson said. 

“I will often remind patients that although you can get your flu shot right away, it does take about two weeks to develop an immune response to that vaccination,” she said. 

“It is important to get your shot as soon as you can to ensure that you have coverage through the flu season.”

Can I get a flu shot and a COVID-19 vaccine at the same time?

For most people, the short answer is yes.

For people age five and older, all seasonal influenza vaccines, including the live-attenuated influenza vaccine, may be given at the same time or before or after other vaccines, including COVID-19 vaccines, according to the most recent recommendations from NACI. 

“It is important that you’re protected from both viruses throughout the winter,” said Davidson. 

WATCH | Experts break down what to expect from flu season this year: 

Daybreak Kamloops7:15Flu season expected to be more intense this year

If there is a year to get the flu shot, this one would be one of them. Experts say we could be in for a severe flu season this fall

However, kids aged six months to five years shouldn’t receive a COVID-19 vaccine and an influenza shot at the same time, according to NACI, which instead recommends those in this age group wait 14 days between COVID-19 shots and other vaccines.

It’s a precautionary approach “to prevent erroneous attribution of adverse events following immunization to one particular vaccine or the other,” reads the committee’s advice. 

How effective are flu vaccines this year?

Experts say influenza vaccines have been proven to help prevent influenza, transmission, complications and hospitalizations. 

The effectiveness of flu vaccines can vary year-to-year because it all depends on the strains circulating, Davidson and Harrison said. 

For the 2004-2005 flu season to 2019-20, Harrison said the effectiveness of influenza vaccines in Canada has varied between around 40 to 70 per cent. 

Every year, World Health Organization (WHO) experts make recommendations on which strains of the influenza virus should be targeted by the vaccines. 

This year, WHO recommended three influenza strains — one influenza A (H1N1); one influenza A (H3N2) and one influenza B — for inclusion in the trivalent flu shot. 

Although the flu vaccine’s effectiveness can vary, both Harrison and Davidson agree that it does offer protection. 

“The effectiveness of the vaccine may not be 100 per cent and may not persist beyond a year, but has impact and that’s why it’s recommended,” Harrison said.


Written and produced by Stephanie Dubois

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Breakthrough Infections More Likely in Infliximab Treated IBD Patients Than Those Treated With Vedolizumab

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Patients with inflammatory bowel disease (IBD) treated with infliximab who were vaccinated against SARS-CoV-2 were more likely to have a breakthrough infection than patients treated with vedolizumab, but the benefits of the vaccine are still superior.

A team, led by Zhigang Liu, PhD, Department of Metabolism, Digestion and Reproduction, Imperial College London, determined how infliximab and vedolizumab affect vaccine-induced neutralizing antibodies against highly transmissible omicron (B.1.1.529) BA.1, and BA.4 and BA.5 (hereafter BA.4/5) SARS-CoV-2 variants.

The Treatments

Anti-TNF drugs, including infliximab, are linked to attenuated antibody responses following SARS-CoV-2 vaccination. The variants included in the analysis have the ability to evade host immunity and with emerging sublineages are currently the dominating variants causing the current waves of infection.

In the prospective, multicenter, observation, CLARITY IBD cohort study, the investigators looked at the effect of infliximab and vedolizumab on SARS-CoV-2 infections and vaccinations in patients with IBD.

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The study included patients aged 5 years or older with an IBD diagnosis that were treated with infliximab or vedolizumab for 6 weeks or longer in infusion units at 92 hospitals in the UK. Each participant had uninterrupted biological therapy since recruitment and were not previously diagnosed with a SARS-CoV-2 infection.

Outcomes

The investigators sought primary outcomes of neutralizing antibody responses against SARS-CoV-2 wild-type and omicron subvariants BA.1 and BA.4/5 following 3 doses of a SARS-CoV-2 vaccine.

The team also investigated the risk of breakthrough infections in relation to neutralizing antibody titers using Cox proportional hazard models.

There were 7224 patients with IBD recruited to the study between September 22 and December 23, 2020. Of this group, 1288 had no previous SARS-CoV-2 infections after 3 doses of the vaccine that were established on either infliximab (n = 871) or vedolizumab (n = 417). The median age of the patient population was 46.1 years.

Following 3 doses of SARS-CoV-2 vaccine, 50% neutralizing titers were significantly lower in the infliximab group compared to patients treated with vedolizumab against wild-type (geometric mean, 2062; 95% CI, 1720–2473 vs geometric mean, 3440; 95% CI, 2939–4026; P <0.0001), BA.1 (geographic mean, 107.3; 95% CI, 86.40–133.2 vs geographic mean, 648.9; 95% CI, 523.5–804.5; P <0.0001), and BA.4/5 (geographic mean, 40.63; 95% CI, 31.99–51.60] vs geographic mean, 223.0; 95% CI, 183.1–271.4; P <0.0001) variants.

Breakthrough infections more frequently occurred in patients treated with infliximab (n = 119; 13.7%; 95% CI, 11.5–16.2) than in those treated with vedolizumab (n = 29; 7.0%; 95% CI, 4.8–10.0; P = 0.00040).

The Cox proportional hazard models show time to breakthrough infection after the third vaccine dose in the infliximab group was associated with a higher hazard risk than treatment with vedolizumab (HR, 1.71; 95% CI, 1.08-2.71; P = 0.022).

There was also higher neutralizing antibody titers against BA.4/5 with a lower hazard risk in the group with a breakthrough infection and a longer time to breakthrough infection (HR, 0.87; 95% CI, 0.79-0.95; P = 0.0028).

“Our findings underline the importance of continued SARS-CoV-2 vaccination programs, including second-generation bivalent vaccines, especially in patient subgroups where vaccine immunogenicity and efficacy might be reduced, such as those on anti-TNF therapies,” the authors wrote.

The study, “Neutralizing antibody potency against SARS-CoV-2 wild-type and omicron BA.1 and BA.4/5 variants in patients with inflammatory bowel disease treated with infliximab and vedolizumab after three doses of COVID-19 vaccine (CLARITY IBD): an analysis of a prospective multicenter cohort study,” was published online in The Lancet Gastroenterology & Hepatology.

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Flu shot uptake in children ‘too low,’ P.E.I. CPHO says

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With flu cases on the rise in the province, P.E.I.’s Chief Public Health Officer is urging parents to get their young children a flu shot.

Currently, just 19 per cent of children under the age of 10 have gotten a vaccine.

“I do think that’s too low,” said Dr. Heather Morrison, the province’s chief public health officer. “On the other hand, we’ve had great uptake of our high dose influenza for those who are 65 years of age and up.”

Morrison said there are some clinics on the weekend in Charlottetown through public health nursing and appointments are available “to really help those who may not be able to come during the week.”

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By Dec. 3 there have been 155 lab-confirmed cases, according to a P.E.I. government website. The median age of cases to date is 14 years old. The site says there was “widespread flu activity” last week on P.E.I. with flu activity “above expected levels for this time of year.”

‘They are getting better now’

Without vaccines, children four and under are most at risk of being hospitalized, Morrison said. That’s exactly what happened to Island resident Shidhin Philip’s youngest son, Adam, who was less than a month old when he was hospitalized with influenza and RSV.

Shidhin Philip’s youngest child, Adam, at the QEH when he was sick with RSV and influenza at less than a month old. (Submitted by Shidhin Philip)

“We were really scared,” said Philip. “But we know we took him to the hospital at the right time, so that was a good decision.”

On Wednesday, Philip brought two of his older children to the children’s clinic in Sherwood to get their flu shot.

“They all had the flu, the sore throat, running nose, they had fever, they were throwing up. They were absent from school for two weeks,” Philip said. “They are getting better now, I don’t want to get it back again. So I took the appointment for the flu shot today.”

A man in a puffy green jacket wraps his arms around his two daughters, who stand on either side of him.
Shidhin Philip and two of his four children, Angel and Anna, outside a vaccination clinic in Charlottetown. (Steve Bruce/CBC)

But he says having vaccines available at public schools would make it easier for busy parents to get their children vaccinated.

“They can send the paper home, we can sign the consent,” he said. “Instead of making an appointment or waiting [a] long time, you know, it can finish in one day.”

Morrison says there are some logistical issues with making the vaccine available in schools, but it is something the province is potentially looking into for future years.

“It’s something that we certainly would be very open to having that conversation with education, public health, nursing, Health P.E.I,” she said. “It has been something that has been discussed over the years.”

In the meantime, she encourages parents to make an appointment and hopes strong messaging, combined with the recent spike in flu cases, will motivate parents to book their kids’ shots.

“Children are at school, and activities, we’re all busy,” she said. “But if we can get it now, get our children vaccinated, ourselves vaccinated, it will protect us in time for the holidays.”

Visit P.E.I.’s weekly influenza summary and flu vaccination clinics websites for more information.

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SARS-CoV-2 Seroprevalence Grew Rapidly in Canada

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Editor’s note: Find the latest COVID-19 news and guidance in Medscape’s Coronavirus Resource Center.

By August 2022, 2½ years into the COVID-19 pandemic, most children and adults younger than 60 years had been vaccinated against SARS-CoV-2 or showed evidence of having been infected by the virus, new data suggest.

A Canadian seroprevalence study of almost 14,000 people found that fewer than 50% of people older than 60 years (the age group that is most vulnerable to severe outcomes) showed evidence of immunity from infection or had been vaccinated by August 2022. Older adults, who have the lowest infection rates but are at highest risk of severe outcomes, should continued to be prioritized for vaccination, according to the authors.

The data were published online December 5 in the Canadian Medical Association Journal.

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Children Most Affected

Previous evidence suggests that a combination of infection and vaccination exposure may induce more robust and durable hybrid immunity than either infection or vaccination alone, study author Danuta Skowronski, MD, MHSc, an epidemiologist at the British Columbia Centre for Disease Control in Vancouver, told Medscape Medical News.



Dr Danuta Skowronski

“Our main objective was to chronicle the changing proportion of the population considered immunologically naive and therefore susceptible to SARS-CoV-2,” she added. “It’s relevant for risk assessment to know what proportion has acquired some priming for more efficient immune memory response to the virus, because that reduces the likelihood of severe outcomes.” Standardized seroprevalence studies are essential for informing COVID-19 response, particularly in resource-limited regions.

The investigators analyzed anonymized residual sera from children and adults in an outpatient laboratory network in British Columbia’s Greater Vancouver and Fraser Valley region. They used at least three immunoassays per serosurvey to detect antibodies to SARS-CoV-2 spike (from vaccine) and to nucleocapsid antibodies (from infection).

The researchers determined any seroprevalence (vaccine-induced, infection-induced, or both) on the basis of a positive finding on any two assays. Infection-induced seroprevalence was also defined by dual-assay positivity but required both antinucleocapsid and antispike detection. Their estimates of infection-induced seroprevalence indicated considerable underascertainment of infections by standard case-based surveillance reports.

During the first year of the pandemic, when public health measures to curtail viral transmission were in place, the study population’s seroprevalence rate was less than 1% for the first three measurements. It was less than 5% by January 2021. With age-based vaccine rollouts, however, seroprevalence increased dramatically during the first half of 2021 to 56.2% by May–June 2021 and to 83% by September–October 2021. More than 85% of the population remained uninfected.

Infection-induced seroprevalence was less than 15% in September–October 2021 until the arrival of the Omicron waves, after which it rose to 42.5% by March 2022 and 61.1% by July–August 2022. Combined seroprevalence from vaccination or infection was more than 95% by the summer, with most children, but fewer than half of adults older than 60 years, showing evidence of having been infected.

“We found the highest infection rates among children, closely followed by young adults, which may reflect their greater interconnectedness, including between siblings and parents in the household, as well as with peers in schools and the community,” the authors write. They note that the low cumulative infection rates among older adults may reflect their higher vaccination rates and greater social isolation.

US data show similar age-related infection rates, but data among children from other Canadian provinces are limited, the authors write.

Broadly Applicable Findings

Commenting on the study for Medscape, Marc Germain, MD, PhD, vice president of medical affairs and innovation at Héma-Québec in Quebec City, said that the pattern observed in British Columbia is representative of what happened across Canada and the United States, including the sweeping effect of the Omicron variant and the differences in impact according to age. “But regional differences might very well exist — for example, due to differential vaccine uptake — and are also probably related in part to the different testing platforms being used,” he said. Germain was not involved in the study.



Dr Marc Germain

Caroline Quach-Thanh, MD, PhD, a pediatrician and epidemiologist-infectologist at the University of Montreal, pointed out that in Quebec, seroprevalence surveys that were based on residual blood samples from children and adults who visited emergency departments for any reason showed higher rates of prior infection than the British Columbia surveys. “But Dr Skowronski’s findings are likely applicable to settings where some nonpharmacological interventions were put in place, but without strict confinement — and thus are likely applicable to most settings in the US and Canada.” Quach-Thanh was not involved in the study.



Dr Caroline Quach-Thanh

She added that the use of residual blood samples always entails a risk for bias, “but the fact that the study method was stable should have captured a similar population from time to time. It would be unlikely to result in a major overestimation in the proportion of individuals positive for SARS-CoV-2 antibodies.”

A recent global meta-analysis found that while global seroprevalence rates have risen considerably, albeit variably by region, more than a third of the world’s population is still seronegative to the SARS-CoV-2 virus.

The Public Health Agency of Canada and the Michael Smith Foundation for Health Research provided funding for the study. Skowronski has received institutional grants from the Canadian Institutes of Health Research and the British Columbia Centre for Disease Control Foundation for Public Health for other SARS CoV-2 work. Germain and Quach-Thanh have disclosed no relevant financial relationships.

CMAJ. Published online December 4, 2022. Full text

Diana Swift is a freelance medical journalist based in Toronto.

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