The vaccine prevents that stress on the body.
Each winter, a familiar tension resurfaces: a virus that kills thousands and hospitalizes children by the tens of thousands, met by a vaccine that many still misunderstand or distrust. In Australia, where 1,744 people died from influenza in 2025 alone, two infectious disease experts have stepped forward to clear the fog — not with alarm, but with evidence. The distance between what people fear about the vaccine and what the science actually shows is, in the end, the most consequential gap of the season.
- Australia recorded 1,744 influenza deaths in 2025, and thousands of children — more than half with no prior health conditions — were hospitalized, making the stakes of vaccine hesitancy concrete and urgent.
- The most stubborn misconception — that the flu vaccine causes flu — persists because post-injection fatigue and soreness mimic early flu symptoms, blurring the line between immune response and infection in people's minds.
- Fears about immune overload, pregnancy risks, and simultaneous vaccine combinations continue to deter uptake, despite robust evidence that none of these concerns reflect how immunity actually functions.
- Health authorities are pushing annual vaccination for every Australian child from six months of age, backed by data showing a 65% reduction in infection risk and a new nasal spray option now available for children aged two to seventeen.
- The science is landing clearly: the vaccine is safe in pregnancy, cannot transmit flu, and does not strain the immune system — leaving public misconception, not medical uncertainty, as the primary barrier to protection.
Winter arrives in Australia carrying a familiar anxiety — and a familiar death toll. In 2025, influenza claimed 1,744 lives and sent thousands of children to hospital, with more than half of those hospitalized children having been perfectly healthy beforehand. Between 2018 and 2023, at least twenty-nine Australian children died from the virus, roughly half of them with no prior illness. Yet the vaccine designed to prevent these outcomes remains clouded by persistent misconception.
Flu is not a bad cold. Controlled studies show it produces more severe, longer-lasting symptoms than other respiratory infections. More dangerously, it strips the lungs of their natural defenses, opening the door to bacterial pneumonia. It can trigger heart attacks and strokes, cause seizures in young children through sudden fever, and in rare cases invade the brain or heart directly. For the elderly managing chronic illness, the infection's stress alone can cascade into organ failure.
The most enduring fear — that the vaccine causes flu — rests on a misunderstanding of its contents. Injectable vaccines contain no live virus, only a surface protein that trains the immune system. The soreness, fatigue, and muscle aches people feel afterward are immune responses to that harmless protein, not flu itself. The nasal spray, newly available in Australia for children aged two to seventeen, uses a weakened virus that replicates only in the nasal passages and cannot produce serious illness.
Concerns about immune overload are similarly unfounded. The body encounters hundreds of antigens daily from food, skin bacteria, and gut flora alone. A flu vaccine introduces only a handful. Multiple vaccines given simultaneously — as is standard in childhood immunization schedules — show no evidence of damaging immune function. In pregnancy, a review of forty studies found no link to birth defects or stillbirth; vaccinated mothers actually showed lower rates of preterm birth, and antibodies cross the placenta to protect newborns too young to be vaccinated themselves.
For children, the vaccine reduces infection risk by roughly sixty-five percent. It is free for many high-risk groups and widely available. The virus kills, hospitalizes, and disables. The vaccine prevents those outcomes. The only real obstacle that remains is the fog of misconception itself.
Winter arrives, and with it comes the familiar anxiety about flu season. In Australia, that worry is not unfounded—last year the country recorded 1,744 deaths involving influenza, and the virus sends thousands of children to hospital annually. Yet alongside the genuine risk sits a fog of misconception about the vaccine itself, the very tool designed to prevent the worst outcomes. Two leading infectious disease experts from Australian universities have spent considerable time answering the questions that keep people from getting protected.
The flu is not simply a bad cold. Controlled studies, where volunteers are deliberately exposed to the virus, show influenza produces more severe symptoms that persist longer than other respiratory infections. What makes it dangerous is what happens next. The virus damages the lungs' natural defenses, creating an opening for bacterial or fungal pneumonia to take hold. The infection can also trigger heart attacks and strokes in vulnerable people. In young children, a sudden fever spike can cause seizures. In rare cases, the virus itself invades other organs—the brain, causing encephalitis, or the heart, causing myocarditis—with devastating consequences. Older people, especially those already managing chronic illness, may simply lack the physical reserves to weather the infection; the stress can trigger confusion, dehydration, and organ failure. The groups at highest risk are at opposite ends of life: infants and young children on one end, elderly people on the other.
Children are not spared. Of roughly half a million flu cases diagnosed in Australia in 2025, about two in five occurred in people under eighteen. Thousands of those children ended up hospitalized. What's striking is that more than half of the hospitalized children had no underlying health conditions—they were healthy before the flu found them. Between 2018 and 2023, at least twenty-nine Australian children died from influenza, and roughly half of those deaths occurred in children with no prior illness. A flu vaccine reduces a child's risk by about sixty-five percent, meaning two out of three vaccinated children will avoid infection or serious complications. For that reason, health authorities recommend vaccination every year for every Australian child from six months of age onward.
The most persistent fear is that the vaccine itself causes flu. This misunderstanding rests partly on confusion about what the vaccine actually contains. Injectable flu vaccines contain no live virus at all—only a purified protein from the virus's surface, called haemagglutinin. When injected, this protein trains the immune system to recognize and fight the real virus if it ever arrives. The side effects people experience—soreness at the injection site, fatigue, headache, muscle and joint pain—are not flu symptoms but rather the body's immune response to that harmless protein. They can feel like flu is starting, which is where the confusion begins. The nasal spray vaccine, newly available in Australia this year for children aged two to seventeen, works differently. It contains a weakened live form of the flu virus that can only replicate in the nose, not in the lungs or deeper airways. More than half of children who receive it develop a runny or blocked nose; about one in ten develop a fever or headache. These are local immune responses in the nasal passages, not signs of actual flu infection. The weakened virus cannot cause the serious illness or complications that real influenza produces.
Another concern—that vaccines might overwhelm the immune system—misunderstands how immunity works. Every day, the human body encounters hundreds of different antigens, the small components that trigger immune responses. Studies show healthy people have measurable immune responses to hundreds of antigens in food alone, not counting the constant exposure from skin bacteria, gut flora, and natural infections. A flu vaccine introduces only a handful of antigens. The idea that this small dose could overload immunity doesn't hold up. In fact, multiple vaccines are routinely given together. The standard childhood immunization schedule typically recommends two to four vaccines at once. Adults are now advised to receive flu shots simultaneously with COVID boosters or the new RSV vaccine. There is no evidence that any of these combinations overwhelm or damage immune function.
Pregnancy presents a special case, but the evidence is reassuring. Pregnant women, their unborn babies, and newborns all face elevated risk of flu complications. A systematic review of forty studies found no link between injectable flu vaccine in pregnancy and birth defects or stillbirth. In fact, vaccinated pregnant women showed lower rates of preterm birth and low birthweight. The vaccine protects the mother directly, and antibodies pass through the placenta to protect the developing baby and the newborn after birth. Infants younger than six months cannot be vaccinated effectively, but maternal antibodies provide a shield during those vulnerable early months.
As winter settles in, the choice is straightforward. The flu vaccine is effective, free for many high-risk groups, and widely available. It cannot give you flu. It cannot overload your immune system. It is safe in pregnancy. For children, it reduces the risk of infection and serious complications by roughly two-thirds. The virus itself kills, hospitalizes, and disables. The vaccine prevents those outcomes. The fog of misconception is the only real obstacle remaining.
Notable Quotes
The flu weakens the natural defences of the lung, allowing bacterial or fungal infection to become established, leading to secondary pneumonia.— Professor Christopher Blyth and Professor Allen Cheng
More than half of hospitalized flu cases in children occur in healthy children with no underlying health conditions.— Research cited by Professors Blyth and Cheng
The Hearth Conversation Another angle on the story
Why do people keep thinking the vaccine gives them the flu when the science is so clear it doesn't?
Because the timing and the symptoms create a perfect storm of confusion. You get the shot, and within hours or a day you feel achy, tired, maybe feverish. Your brain connects those dots and thinks, "I got the flu from the vaccine." But what's actually happening is your immune system is waking up and responding to the protein in the vaccine. It feels like illness because inflammation feels like illness.
So the side effects are actually a sign the vaccine is working?
Not exactly. The side effects mean your immune system is responding, which is necessary for protection. But you can have a strong immune response without side effects, and you can have mild side effects and still get good protection. They're not a measure of effectiveness.
The nasal spray vaccine is live virus though. How is that safe?
It's weakened so severely it can only replicate in the cool, moist environment of the nose. It can't survive in the warmer, deeper parts of the lungs where real flu causes damage. So you get a local immune response in the nose—runny nose, maybe a low fever—but the virus never establishes the kind of infection that causes pneumonia or organ damage.
What about the argument that vaccines overload the immune system? That seems intuitive, doesn't it?
It does, but it's based on a misunderstanding of scale. Your immune system encounters hundreds of different antigens every single day just from food, from bacteria on your skin, from the air you breathe. A vaccine introduces a handful. It's like worrying that adding a few grains of sand will overwhelm a beach.
The pregnancy data surprised me—that vaccinated women had better outcomes.
It did surprise many people. But it makes sense when you think about it. Flu in pregnancy is genuinely dangerous. It can trigger preterm labor, low birthweight, all kinds of complications. The vaccine prevents that stress on the body. And the mother's antibodies protect the newborn during those first months when the baby is too young to be vaccinated.
So what's the real barrier to vaccination, if not safety?
Often it's just inertia and noise. People hear conflicting information, they're busy, they think "I'm healthy, I don't need it." But the data on children is sobering—half the kids hospitalized with flu had no underlying conditions. They were just unlucky. The vaccine doesn't eliminate that risk entirely, but it cuts it by two-thirds.