Influenza

Influenza, also commonly known as the flu, is an infection of the respiratory tract caused by viruses affecting the nose, throat, and sometimes the lungs. These viruses are classified into 4 types: A, B, C, and D; however it is influenza types A and B that most often cause illness in humans.

Simple ways to control flu spreading is:

• Annual flu vaccination
• Staying home if unwell
• Washing your hands frequently with soap and water
• Wiping over frequently touched surfaces

Use a mask and tissues and cover your mouth when coughing or sneezing.

The flu spreads easily through families, workplaces, childcare centres and schools:

• when an infected person coughs or sneezes, and you breathe it in
• through direct contact with fluid from an infected person’s coughs or sneezes
• by touching a contaminated surface with the flu virus on it, and then touching your mouth, eyes or nose.

Symptoms usually start about 1 to 4 days after catching the flu and can last for a week or more. Some people can be mildly affected, while others can become seriously ill.

If you have the flu, you can be infectious to others from 24 hours before symptoms start until 1 week after the start of symptoms.

Flu symptoms include:

• Fever
• Headache
• Chills
• Cough
• Body pain or muscle pain
• Fatigue
• Sore throat
• Runny nose
• Sneezing
• Reduced sense of smell
• Metallic taste in mouth
• Vomiting and diarrhoea (more common in children).

Complications may include:

• Pneumonia
• Encephalitis
• Myocarditis
• Myositis
• Kidney failure
• Sinusitis and middle ear infection (less serious but more common complications)

• Babies
• Older than 65 years
• Aboriginal and Torres Strait Islander people
• Pregnant women
• Individuals with long-term medical conditions
• Individuals  suffering from respiratory problems such as asthma, chronic obstructive pulmonary disease
• Individuals with chronic medical conditions such as diabetes, cancer
• Individuals who have weakened immune systems
• Individuals who are obese or who smoke
• Individuals who haven’t been vaccinated against the flu.

• Usually diagnosed by symptoms and/or known contact with someone who has the flu
• Definitive diagnosis is by swabbing nose and throat or blood test for the virus

The recommended treatment is rest, drinking plenty of fluids and use of paracetamol for the relief of pain and fever. You should see your local doctor if you are concerned about your symptoms or if your symptoms are getting worse. Antiviral medication may be prescribed by your doctor if you are at risk of complications from the flu, but it does need to be started within 48 hours from the onset of flu symptoms. Antibiotics are not effective for treating the flu.

Your symptoms may include headache, muscle aches, rapid onset of fever, fatigue, sneezing, running nose, sore throat, and cough.

Antibiotics are ineffective against the influenza virus, and so in severe flu cases and for people at risk of complications, antiviral medications may be prescribed.

Annual flu vaccination is recommended for any person from six months of age who wishes to reduce the chance of being ill with the flu. For anyone in a high-risk category, the flu can be a serious and potentially fatal illness.

The National Health and Medical Research Council strongly recommends annual vaccinations for people with:

• Heart disease
• Asthma
• Lung disease
• Diabetes
• Kidney or liver disease
• Impaired immunity
• Pregnant women
• Chronic neurological disorders (such as Multiple sclerosis)
• Metabolic disorders
• Blood diseases

The vaccine is composed of inactivated or dead viruses, and so, despite claims, it does not actually cause the flu. However, it is understandable that some people may be concerned about this risk as up to 10% of recipients may develop fever, fatigue and muscle aches. These symptoms will last only a few days, whereas influenza can make you unwell for far longer.

You can still get the flu vaccine if you have a mild illness, such as a cold or sinus infection. People who have a fever or a moderate or severe illness may need to delay vaccination until they've recovered. If you're sick and are unsure if you should receive a flu shot, talk to your doctor about your symptoms.

Generally, if there are any mild reactions, they will begin within 6 to 12 hours.

Post-vaccination symptoms may mimic influenza infection, however, are generally mild and may include: pain, redness and swelling at the injection site, fever, lethargy and muscle aches.

Studies have shown that people over the age of 65 years who have received either the high dose or adjuvanted flu vaccines experience slightly higher rates of injections site reactions compared to the other formulations. There were also more mild/moderate systemic reactions reported among the high-dose recipients.

Adverse events from cell-based vaccines occurred at similar rates to the standard flu vaccines, with only slightly higher rates of injection site reactions.

As with any medication, there is a rare risk of having a severe allergic reaction that usually occurs within 15 minutes of receiving the vaccination. For this reason, it is important for you to wait for 15 minutes after receiving the vaccination before leaving the immediate area.

As with all vaccinations and medication, there is the possibility of an anaphylactic reaction. These reactions are rare when the following groups are excluded through pre-vaccination screening:

• Individuals who have previously reacted to the vaccine or a vaccine component
• Individuals who have ever had Guillain-Barré Syndrome
• Individuals with a history of anaphylaxis or a severe reaction to eggs or egg products, although an allergy to eggs is not a contraindication to influenza vaccination.

Yes. The flu vaccination can be safely given during any stage of pregnancy. Pregnant women are at an increased risk of severe disease or complications from the flu. Vaccinating against the flu during pregnancy can not only protect pregnant women but provide ongoing protection to a newborn baby for the first six months after birth.

As with other people pregnant women can experience side effects from the influenza vaccine, including:

• Redness and swelling at the injection site.
• Fever
• Headache
• Nausea
• Aching muscles
• Tiredness

In general, any side effects experienced after receiving an egg-based influenza vaccine will usually start soon after the injection administered and last for 24 to 48 hours – the same applies when the vaccine is administered during pregnancy. Studies have not shown any adverse birth outcomes for the baby when the flu vaccine is administered during pregnancy, and in fact it offers protection to the baby as flu infection in the mother can be harmful for her unborn child. With cell-based flu vaccines, Australian immunisation experts have stated, ‘there are no theoretical concerns regarding their safety in pregnant women’.    

The Australian Technical Advisory Group on Immunisation (ATAGI) has advised that influenza vaccines can be given at the same time as COVID-19 vaccines.

No, each disease is caused by a different virus, so the COVID-19 vaccine will not protect you from contracting the flu.

The best way to protect yourself from days off work, or spending time in bed feeling very sick and passing it on to others, is to be vaccinated against influenza viruses. But, no, in general the flu vaccine is not mandatory, but it may be required for people working with vulnerable groups. It is, however, highly recommended since it is very effective and safe.  If more people are immunised against the flu and other vaccine-preventable diseases, the less chance they can spread in the community.

The Australian Immunisation Register (AIR) records the vaccines all people in Australia receive so there’s no need to add your vaccination history to the AIR since it’s done automatically by the provider if you’re enrolled in Medicare.

Influenza vaccine formulations change each year as the flu virus mutates (antigenic drift), so the vaccine used in the last year may well be different to the one for this year. The Australian Influenza Vaccine Committee (AIVC) reviews epidemiology data, genetic and antigenic characteristics of the isolates circulating in Australia and the Southern Hemisphere. The flu strains predicted to affect Australians are reviewed and the available vaccines changed according to the strains.

For example, based on this review and the WHO’s recommendation, the AIVC recommended the viral strains to be used for the 2022 southern hemisphere influenza season to include the addition of a new A (H3N2)-like flu strain and a new B Victoria-like strain.

The egg-based quadrivalent influenza vaccines for 2022 cover the following 4 viral strains:

• an A/Darwin/9/2021 (H3N2)-like strain
• an A/Victoria/2570/2019 (H1N1)pdm09-like strain
• a B/Phuket/3073/2013 (B/Yamagata lineage)-like strain
• a B/Austria/1359417/2021-like (B/Victoria lineage) strain

Cell-based quadrivalent influenza vaccines contain the following 4 viral strains:

• an A/Wisconsin/588/2019 (H1N1)pdm09-like strain
• an A/Darwin/6/2021 (H3N2)-like strain
• a B/Austria/1359417/2021 (B/Victoria lineage)-like strain
• a B/Phuket/3073/2013 (B/Yamagata lineage)-like strain.

Flu vaccine development began about one hundred years ago. In the 1930s, the Influenza A virus was isolated from animals in order to find out how it could be weakened/neutralised for vaccine development purposes. Then:

• In the early 1940s: With support from the US Army, the doctor who developed the polio vaccine, Jonas Salk MD, worked with others to produce the first inactivated flu vaccine. The Army’s effort was in response to the mass casualties suffered during the 1918 flu pandemic in the wake of World War 1.
• 1942: An Influenza A and B vaccine was developed after the B strain was discovered.
• 1945: The first Influenza A vaccine was licensed in the US.

The science is still based on the discoveries of 100 years ago, although the vaccines now cover 2 types of influenza A and 2 of influenza B viruses. New technology has emerged and there are more developments in the pipeline.

Influenza is a very contagious respiratory disease, and the vaccines are crucial to keeping people safe and healthy. But how long does it take for the jab to take effect?  About a fortnight on average for the vaccine to effectively offer good protection against contracting the flu. By choosing to be vaccinated, you protect yourself, your loved ones and the vulnerable members of your community.