The Flu Vaccine - Do We Really Need It? What Science Says

General Medical

Tammy George

Woman sick with the flu blowing her nose.
Warnings about the impending flu season are everywhere in autumn. Health experts worldwide, recommend the flu vaccine to keep us safe from the influenza virus and its potentially deadly health complications. 

Between 5-20% of the world's population is struck down by the flu each year. Around 36,000 people in the US alone die from the flu and its complications every year, and another 200,000 are hospitalised because of the flu. Australia had one of its worst flu seasons in 2019 after a mild season in 2018 left more people vulnerable. But can the flu vaccine really stop you being struck down?  

What Is the Flu Vaccine?

The flu vaccine works by stimulating your immune system to produce antibodies. Antibodies are proteins that attack germs, such as the flu virus. It can take up to two weeks for your body to build up antibodies after you have had the flu shot. 

Each year the vaccine is developed after researching what strain of influenza is most likely to circulate in the upcoming season. They then grow the virus in eggs. The vaccine is most commonly given as an injection in the arm. 

Young man receiving the flu vaccination in his arm by a registered nurse.

How Many Types of the Flu Shots Are There?

There are different influenza vaccine manufacturers and different types of vaccine products available. The most common vaccines are:

Trivalent Vaccines: 

  • A standard-dose shot made with adjuvant (ingredient added to helps create a stronger immune response), registered for use in people aged 65 years and older.
  • A high-dose shot (containing four times the antigen of a standard-dose shot), registered for use in people aged 65 years and older. 

Quadrivalent Vaccines: 

  • A standard-dose shot, designed to protect you from four strains of influenza. Manufactured with the viruses grown in eggs. This vaccine is licenced for children as young as 6 months of age.
  • A cell-based shot, all viruses used in the vaccine are grown in cells, making the vaccination completely egg-free. Only licenced for people 4 years and older in the United States.
  • A recombinant-based shot, recombinant vaccines are created synthetically. Licenced in the United States, approved for people aged 18 years and older. Completely egg-free.

Immunisers give the majority of the population quadrivalent, which protects against four different flu viruses:

  • Influenza A (H1N1)
  • Influenza A (H3N2) 
  • Two influenza B viruses

Quadrivalent in more detail is an inactivated vaccination, meaning it doesn’t contain a live virus. Instead it contains killed, weakened or influenza components. You can read more about Influenza vaccines available in Australia in the Australian Immunisation Handbook

The second main flu vaccine is trivalent which is licensed for people over the age of 65. It contains four times the antigen of a standard inactivated flu vaccine. It triggers a stronger immune response to provide better protection against the flu. Older adults have weaker immune systems and may also have a lower immune response to the flu vaccine, so they require a stronger dose. A study has found the high-dose trivalent is 24.2% more effective in preventing flu in older adults than the standard-dose. Trivalent is also an inactive vaccination.   

Types of Influenza Viruses/ Strains 

The different strains of flu are identified by a code. 

The H refers to hemagglutinin (Ha or H) and N refers to neuraminidase (Na or N). Both are viral molecules that attach to the outside of viral particles. The Ha invade cells in our respiratory tract while the Na works by bursting out of cells and invading others. 

There are 4 types of seasonal influenza viruses. However, Influenza A and B are the main viruses that circulate during flu season. Strains C and D are less frequent. Influenza C usually is mild and is not seen as a threat. Influenza D mainly affects cattle and is not known to cause illness in people.

Petri dish showing the different types of Influenza viruses.

Ideal Flu Vaccine Timing

Health authorities recommend having the flu vaccination early in the fall, just before the virus is widespread in the community. Also, your body needs two weeks following the injection to start producing antibodies, it needs to protect you. 

How Effective Is the Flu Vaccination? 

The Centers for Disease Control (CDC) calculated the flu vaccine prevented 6.2 million flu illnesses during the 2017/18 season. It also prevented an estimated 3.2 million medical visits, 91,000 hospitalisations and 5,700 flu associated deaths. 

A 2018 study showed flu vaccinations reduced the risk of adults being admitted to ICU with the flu by 82%. A study in 2014 revealed vaccines reduced the risk of pediatric intensive care unit admissions by 74% during 2010-2012 flu seasons.  

The chance of you contracting the flu after vaccination depends on two main factors:

  • Your characteristics such as age and health
  • The match between the flu vaccine and flu viruses spreading through the community. 

Every year the flu vaccine’s ability to prevent influenza changes based on how well the vaccine is matched to the circulating viruses. When it’s a good match, the flu vaccine can reduce the risk of visiting the doctor for the flu by 40-60%. 

Flu vaccines usually work best against influenza B and influenza A (H1N1) viruses, but offer lower protection against influenza A (H3N2) viruses.  

The vaccine can be life-saving for the most vulnerable, including people over the age of 65 and those who suffer from chronic illnesses such as lung disease, heart disease and diabetes.

Who Should Be Vaccinated Against the Flu?

Health authorities around the world recommend almost everyone aged over six months should get an annual flu vaccination. The vaccine is the best way of avoiding the flu and its health complications. By having a flu shot, you are protecting yourself, minimising the spread of flu and protecting vulnerable groups in the community, including babies under the age of six months who are too young to receive the vaccine.   

A pregant mother and her toddler in the kitchen, they are most at risk during the flu season.

Some people in the community are at greater risk of catching the flu. People aged over 65 often have weaker immune systems and are at greater risk of developing complications from the flu. Young children under the age of five are also at greater risk of serious health problems from the flu. Pregnant women and immune-suppressed people are also advised to have the flu vaccination.

Who Should Not Be Vaccinated Against the Flu?

There's only a small percentage of the world's population who shouldn’t have the flu vaccine. 

Children under the age of six months are too young for vaccinations however, young babies are at high risk of developing serious complications from the flu. 

Doctors may recommend people with a life-threatening allergy not to have the flu vaccine, but should speak to their doctor directly. An egg allergy may only require you to have the vaccine at a doctors surgery, where you can be monitored for any reaction. 

People who’ve had the severe autoimmune condition, Guillain-Barré Syndrome, shouldn’t have the flu vaccine. 

You should always delay getting the flu vaccine if you're feeling unwell or have a fever. 

Is It Safe for Children to Be Given the Flu Vaccination?

Yes, it’s safe for children over the age of six months. In some areas, children under the age of ten must see a GP for their flu vaccination, while older siblings and parents can have the flu vaccine anywhere. 

Young toddler sick with the flu, with thermometer in his mouth.

Two Doses for First Time Children

A child who has never been vaccinated for the flu and is aged between six months and eight years (or younger depending on the area) may be required to have two flu shots. They’re given the injections at least four weeks apart. Only one shot is required for all subsequent flu seasons.   

How Does the Flu Kill People?

The flu can directly cause death, or it causes other serious health problems, which can lead to death. Death can occur quickly, when flu is the direct cause and death from secondary infections after contracting the flu can occur from one week. 

Multi-organ failure is a direct cause of flu-related deaths. The respiratory and kidney systems can stop functioning properly. When there is severe inflammation in the lungs, oxygen can’t pass through the lungs into the blood and can result in death. An extreme body-wide inflammatory response can lead to sepsis.

Serious complications of the flu include pneumonia and inflammation-related disorders of the heart (myocarditis), brain (encephalitis) or muscle (myositis, rhabdomyolysis) tissues.  

Existing serious health problems can also worsen with the flu. Some strains of the flu can cause more severe symptoms than other strains.      

Should I Have a Flu Vaccine Every Year?

The influenza virus mutates each season, so the flu vaccine changes yearly to protect against the strains most likely to cause an outbreak. The vaccine you had last year may not provide any protection against the influenza strains this year. 

Also, your immunity drops over time, so after three to four months you might not be immune anymore. Older people are more at risk of losing their immunity towards the end of the flu season, more than a younger person.

How Do I Know If I’ve Ever Had the Flu?

Some people use the word ‘flu’ interchangeably for a cold. But the two are very different caused by separate viruses. 

Flu Symptoms

The flu is most common in winter and early spring. The symptoms include: 

  • Fever
  • Chills
  • Cough
  • Sore throat
  • Tiredness
  • Muscle aches

Vomiting, diarrhoea (sometimes with children)

Young girl sick at home on the couch with the flu, symptoms include runny nose, fever and headaches.

Will I Get Cold or Minor Flu Symptoms From the Flu Vaccination?

The flu and cold viruses are different so you can’t get a cold from having the vaccine, however, some people suffer vaccine side effects that are similar to a cold.  

The most common side effects include:

  • Red or swollen area at the site of injection
  • Fever
  • Cough 
  • Sore throat 
  • Runny or stuffy nose
  • Body aches 
  • Headache 
  • Chills and fatigue

Can I Get a Severe Reaction to the Flu Vaccinations?

Severe reactions to the flu vaccination are extremely rare. There’s a small chance of an allergic reaction to the injection, so patients often wait for 15 minutes after the shot in case of a reaction. The symptoms of a severe allergic reaction include:

  • Difficulty breathing
  • Hoarseness or wheezing
  • Swelling on the face
  • Hives
  • Paleness
  • Feeling weak
  • Fast heart beat or dizziness 

Does the Flu Vaccination Guarantee You Won’t Catch the Flu?

There are no guarantees with influenza. It’s still possible to catch the flu after the vaccination. There is the chance that you’re already infected before having the vaccine, or you catch it within the first two weeks after the injection. It’s still possible to catch the flu after the two weeks, but the vaccine should reduce the severity of the infection, so the chance of severe symptoms are far less likely.  

How Else Can I Protect Myself Against the Flu Virus? 

The flu virus can be hard to avoid. Around 20-30% of people carrying the influenza virus have no symptoms, so it’s not obvious who you can and can’t catch the virus from. 

While the vaccine offers excellent protection, there are other measures you can take to keep yourself safe from the flu. 

Limit Close Contact

If a family member or friend is sick, try to stay a distance away to protect yourself. If you can, move to another room to sleep and don’t sit too close. Don’t share utensils or glasses until they are washed. 

Pair of hands with soap being cleansed to prevent the flu.

Regular Hand Washing

Washing your hands with soap and water will remove a flu or cold virus you may pick up from a contaminated surface. If you don’t have access to soap or water, use an alcohol-based hand sanitizer. 

Stop Touching Your Face

The flu virus enters our bodies through the respiratory tract so it’s best to not touch your mouth, nose or eyes in case you have the virus on your hands. This is particularly important when you are out in public and touching surfaces like lift buttons, handrails and door handles that many people may have touched or coughed on.    

Clean Surfaces

If a family member is sick, try to keep common surfaces like light switches, door handles and bench tops clean by disinfecting them regularly.  

What to Do if You Get the Flu

If you’re struck down with the flu, try not to pass it on to others. Cough and sneeze into a tissue, throw it in the bin and wash your hands with soap and water. Try not to touch other people and stay away as much so you aren’t breathing (sneezing or coughing) over them. 

Fluids and Rest

It’s easy to become dehydrated when you have the flu, so drink plenty of fluids such as water, fruit juice and soup. Bed rest will help your immune system fight the infection. If you have a sore throat or aches and pains, take pain relief medication. 

Medication for the Flu

You can lessen the severity and length of your illness by taking over-the-counter cold and flu medications, but see a doctor if your symptoms worsen. 

People Most at Risk of Contracting the Flu

People most at risk of complications from the flu include those with:

  • Diabetes
  • Heart disease
  • Cancer
  • Liver, kidney or metabolic disorders
  • Blood disorders
  • Weakened immune system
  • Lung disorders and asthma.  

Other people in the community at risk include:

  • Pregnant women or mothers who have given birth in the last two weeks
  • Over the age of 65
  • Children under two years (under six months are the most vulnerable)
  • People living in long-term care facilities

Mother holding newborn baby who is at risk of being exposed to the flu virus.

If you suffer from any major health conditions, see your doctor as soon as you notice symptoms of the flu. Your doctor may prescribe antiviral drugs, which help fight bacterial infections. These drugs are a second line of defence after the flu vaccine. 

If you take antiviral drugs within the first two days of the flu infection, they can:

  • Reduce the incidence of ear infections in children 
  • Minimise the chance of needing hospitalisation for adults
  • Reduce the chance of respiratory complications that need antibiotics
  • Reduce the risk of death  

Is a Long Lasting Flu Vaccine Available Yet?

Researchers at the University of Nebraska–Lincoln have developed a new vaccine that could provide life-long protection as the flu. The team traced the ancestral flu virus to find the shared genes of modern flu viruses. Of the 18 subtypes of flu, they worked with the four most likely to cause disease outbreaks and created a vaccine. Mice were used to test the vaccine, and the study found that even low doses of the vaccine were effective against the high dose of flu virus they infected each mouse with. This type of long-lasting flu vaccine might only be suitable for children. They think up to half of all adults have been exposed to cold viruses that stop the body using the vaccine to build up enough immunity against the flu.    

So Should You Get the Flu Vaccine?

Health authorities around the world continue to encourage everyone over the age of six months to have a flu vaccination yearly at the start of the flu season. The vaccine is your best protection against contracting the flu and its health complications. By having the vaccine, you're helping stop the spread of the virus and protecting people in the community who are less able to recover from the flu and secondary infections. Speak to your doctor or pharmacist about protecting you and your family from influenza this season.

Tammy George

Please note: Tammy's blog is general advice only. For further information on this topic please consult your healthcare professional.

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