We hear it all the time: “I don’t want a flu vaccine. It gives you the flu.“ The old, the young, and even health professionals make this claim. And it’s usually followed by a personal example like, “the year I had a flu vaccine, I got the worst case of flu ever.”
It’s physically impossible for the flu vaccine to cause the flu (influenza) because the vaccines licensed for use in Australia are all inactivated. This means the viral cells in the vaccine have been killed and are not capable of causing infection.
But this belief is persistent – here’s why:
1) The vaccine itself can make people feel a bit under the weather for a couple of days
Although the flu vaccine cannot cause true influenza, it makes 1% to 10% of people feel as if they have a mild flu infection. This is the body mounting an immune response to the vaccine - with some experiencing muscle or joint aches, fever, and tiredness for a day or two.
While these symptoms can be unpleasant and inconvenient, the good news is they are evidence the body is responding to the vaccine and developing immunity. When that person has their annual flu vaccine the following year, the side effects are usually less intense.
2) A person might get another virus that feels like influenza
After getting an influenza vaccine, a person might get another virus they mistakenly believe to be influenza. That virus could be rhinovirus, respiratory syncytial virus, adenovirus, parainfluenza, human metapneumovirus, coronavirus, human bocavirus, polyomavirus, or even one that virologists are yet to discover.
These can all cause flu-like symptoms which might include fever, sore throat, cough, runny nose, and malaise. And because the influenza vaccine only prevents the influenza virus, a person might still get one of these other viruses.
It’s understandable that if a person has a vaccine against influenza and they still get an illness that feels like flu, they may either think the vaccine is not effective or worse, is causing their illness. But it’s not, it’s probably another infection.
3) A person may get a strain of influenza not covered by the vaccine
In some influenza seasons, the strains in the vaccine do not match the circulating viruses as closely as predicted. So a person might develop influenza from a viral strain that was not in the vaccine.
4) Some people’s immune systems don’t respond to the influenza vaccine
Some people don’t develop immunity from the influenza vaccine so they remain vulnerable to getting influenza. Again, the vaccine isn’t causing their disease, it’s just not providing the intended protection.
Age is the biggest factor here and older people’s immune response to the influenza vaccine is not as good as it is in younger people. Does that mean it’s not worth older people being vaccinated? No, because they are the group most likely to die from influenza or its complications.
Making the choice
Any decision about having a flu vaccine should be made in consultation with a health professional. But when doing so, it’s worth considering the facts:
- It’s one of our most lethal diseases. Although the death rate is less than one in 1,000 overall, it especially affects older people and is estimated to kill about 3,000 and hospitalise 13,500 Australians aged over 50 each year.
- It costs our nation A$115 million annually in direct health care costs.
Influenza is often thought of as a disease of the old. But while older people are the group most likely to die from influenza, children don’t escape the toll. In fact, children under five years of age are the group most likely to be hospitalised for influenza. And my research team found families of children with severe influenza suffered significant disruption, distress and reduced quality of life.
Despite its burden, influenza is the underdog of infectious diseases. Its very name conjures up a folksy familiarity that contrasts with our dread of diseases such as polio, meningococcal disease or whooping cough. The mass media rarely feature stories of influenza’s victims – a big motivator of preventive action. In risk perception terms, influenza is a low outrage-high consequence disease: we under-react to it.
The focus on the influenza vaccine’s side effects hasn’t helped. One vaccine, “Fluvax”, caused a much higher rate of febrile convulsions in children aged five years or under in 2010 and is no longer registered for use in this age group. But the influenza vaccine generally has a side effect profile similar to most vaccines. There are common but minor side effects, such as soreness at the injection site, and more rare but serious ones like anaphylaxis.
Next time you are deciding whether a flu vaccine is worthwhile, consider that it that it might just give you some protection from influenza. That benefit is even greater if you are at higher risk of serious complications from this disease (if you’re aged 65 years and over, are an Aboriginal or Torres Strait Islander, have a chronic disease, are pregnant, are obese); or if you’re at risk of getting and passing on influenza through your work (for health care workers), or are planning travel.
And these benefits come with the assurance that the vaccine itself cannot give you influenza.