A Ray of Light Amid a Dark Winter for Sick Kids

Respiratory illnesses are everywhere these days, but why bother getting your kid their flu shot so late in the season? It could pay off years from now.


This winter has come with an early and rapid surge in pediatric hospitalizations for respiratory illnesses in Canada. Children’s ICUs were filled beyond capacity, and in an echo of the early COVID pandemic, pediatric surgeries started being cancelled to open up space.

In addition to COVID cases, flu and RSV admissions added strain to the system. Although there is no vaccine for RSV, it still isn’t too late for kids to be vaccinated against COVID and the flu. Protection starts to build within days and will last the rest of the season and beyond.

It’s worth noting that young children are especially vulnerable to serious flu complications, which include pneumonia, vomiting, and dehydration. While it might seem late in the flu season, researchers at McMaster University have found a little-known benefit for children who get repeated seasonal flu vaccines: they can generate antibodies that give them broad protection against future flu strains. The study was published in Cell Reports Medicine.

A seasonal flu vaccine is needed annually, and its effectiveness varies; to get doses ready in time for vaccination, predictions need to be made about which strains will dominate, and in adults the immune response tends to be strain-specific. Sometimes there is a mismatch between the predictions and what strains are actually circulating, and other times new strains emerge.

The study found that children who got their flu vaccines three years in a row over the course of the study had a special immune response that gave them even higher titres of universal anti-flu antibodies each year. That translates into broad protection that isn’t specific to only the strains included in the seasonal vaccine.

The flu virus has a surface protein called hemagglutinin (HA) that has a head domain that tends to vary by strain, and a more stable stalk domain that is conserved even when new strains evolve.

While adults tend to make antibodies that target the strain-specific head domain, kids were also able to make antibodies that bind to the universal stalk domain. This ability was the strongest in the youngest children who participated in the study, which looked at kids aged 3-15 years old. Both the conventional flu shot and a nasal spray vaccine worked equally well, giving more choices for vaccination.

“This is an important finding because it means we have flexibility in terms of the type of vaccines we can use to make a universal vaccine for children,” said principal investigator Matthew Miller, associate professor of biochemistry and biomedical sciences at McMaster University, in a press release.

“We now know that children’s immune systems are much more flexible than adults’ when it comes to being able to teach them how to make these broadly protective responses.”

The study’s findings come as welcome news, as we know that flu pandemics are a persistent threat, and children are major drivers of transmission. They are also a high-risk group for severe cases.

The other good news is that this year’s flu vaccines are a solid match for the strains in circulation. So no matter your age, it’s not too late to get a flu vaccine to protect yourself this year.

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Karyn Ho is a science animator and engineer who thrives at the interface between science, engineering, medicine, and art. She earned her MScBMC (biomedical communications) and PhD (chemical engineering and biomedical engineering) at the University of Toronto. Karyn is passionate about using cutting edge discoveries to create dynamic stories as a way of supporting innovation, collaboration, education, and informed decision making. By translating knowledge into narratives, her vision is to captivate people, spark their curiosity, and motivate them to share what they learned.