Seasonal flu (also known as influenza) is a highly infectious illness caused by the Influenza Virus.
The virus infects your lungs and upper airways, causing a sudden high temperature and general aches and pains, headache, weakness and exhaustion. Symptoms can last for up to one week. You may need to stay in bed until your symptoms get better. Flu affects people of all ages. In some people flu can cause serious complications such as pneumonia.
Flu is more severe in people aged 65 years and over, pregnant women, and anyone with a long-term medical condition. The HSE is urging people in at-risk groups to get the flu vaccine.
People aged 65 years and over
People (adults and children) with long-term medical conditions such as diabetes, heart disease, liver, kidney disease, cancer, chronic lung disease including COPD, or neurological diseases
People whose immune system is impaired due to disease or treatment including cancer patients
Persons who are obese who have a body mass index (BMI) of over 40
People with Down syndrome
Residents of nursing homes and other long-stay institutions
Carers and household contacts of people at medical risk of the complications of flu
People with regular close contact with poultry, water fowl or pigs
About The Flu Vaccine
The seasonal influenza vaccine provides protection against Seasonal Influenza. The highest incidence of Influenza is between late December and March each winter. The seasonal flu vaccine (flu jab) protects against 4 strains of flu virus. These are the strains most likely to be circulating this flu season. You need to get a new vaccine each year. This is because the strains of the flu virus change.
The vaccine is available for free via the HSE for those with a Medical Card and for those in the at-risk groups above (you may still need to pay for the GP consultation).
If you are not in the at-risk groups (above) you can still get the flu vaccine but the relative benefit (the difference between the risk of flu complications and the risk of complications from the vaccination) is less. If you were to get the flu, you would most likely recover without complications.
The flu vaccine helps your immune system to produce antibodies (proteins that fight infection). If you have had the flu vaccine and you come into contact with the flu virus, the vaccine can stop you from getting sick.
The flu vaccine starts to work within 2 weeks. It will not stop all flu viruses and the level of protection may vary, so it is not 100% effective and you may still get flu. But if you do get flu after you have the vaccine, it is likely to be milder and you will recover more quickly. Flu vaccines usually reduce the risk of infection by 40-60%.
Reactions to the vaccine are generally mild.
There is no thiomersal (mercury), gelatin or porcine gelatin in the 2023/2024 flu vaccine.
You should NOT get the Flu Vaccine if you:
have had a severe allergic (anaphylaxis) reaction to a previous flu vaccine or any part of the vaccine (eggs, neomycin, octoxinol-9).
are taking medicines called combination checkpoint inhibitors, for example, ipilimumab plus nivolumab
are ill with a temperature greater than 38 degrees Celsius - you should wait until you are well before getting the vaccine.
If you have an egg allergy, you should not get the vaccine in an office setting. Instead, talk to your GP about vaccination in a controlled healthcare environment.
Common side effects
You may have a mild fever and aching muscles for a couple of days after having the vaccine. Your arm may also be a bit sore where you got the injection.
Uncommon/Rare side effects
Dizziness, diarrhoea, feeling sick (nausea), fatigue, reactions at the injection site: bruising (ecchymosis), itching (pruritus), and warmth.
Swelling of the glands in the neck, armpit or groin (lymphadenopathy)
Anomalies in the perception of touch, pain, heat and cold (paraesthesia), sleepiness, increased sweating (hyperhidrosis), unusual tiredness and weakness (asthenia), flu-like illness. Joint pain (arthralgia), discomfort at the injection site.
Blood vessel inflammation (vasculitis) which may result in skin rashes and in very rare cases in temporary kidney problems.
Transient thrombocytopenia, lymphadenopathy, paraesthesia
The Seasonal Influenza Vaccine is normally well-tolerated but unwanted effects do occur.
A severe allergic reaction (anaphylaxis) may present as an itchy, lumpy rash with one or more of:
swelling around the face or mouth
If you are very concerned about your symptoms, you should call an ambulance (dial 112) to attend an Emergency Department immediately.
Pain At The Injection Site
It is normal to have mild pain and tenderness at the injection site for up to 2 weeks. No treatment is necessary but you may manage your symptoms with paracetamol or ibuprofen.
If you have severe pain, swelling or bruising that limits your ability to raise your arm, you should attend your GP for an assessment.
Pain Away From The Injection Site
You may experience fever and body aches & pains while your immune system builds it's response to the vaccine. This does not mean that you have the Influenza infection (there is no live virus in the adult flu vaccine). No treatment is necessary but you may take paracetamol or ibuprofen to manage the symptoms.
Read more about uncommon or rare vaccine side effects from the manufacturer here.