This piece was written by one of our contributors; Ireland-trained medical doctor – Ciara Kelly
When Autumn arrives every year, most of us think of falling leaves, Halloween, children heading back to school, and the weather changing from summer sun to seasons of wind, rain, and maybe even snow! However, Autumn also signifies the start of ‘flu season’, a period from October to March/April when influenza, commonly known as ‘the flu’, affects populations in the Northern Hemisphere (including of course Ireland and the U.K.), with outbreaks of illness occurring every year, to varying degrees of severity. Most of you reading this will probably have heard of and/or had the flu – it’s one of the most well-known infectious diseases we see patients present with as doctors.
Unfortunately, there are a LOT of myths and misconceptions about the flu and the vaccine we have to help prevent it. So in this article, we’re going to look at what influenza is, who should get the seasonal influenza vaccine, and most importantly, we’ll bust some common myths about the vaccine itself.
What is influenza?
Influenza is an acute respiratory viral illness, which can cause disease ranging in severity from mild to moderate to severe. In the most severe cases, influenza can result in death.
The symptoms of influenza are typically of sudden onset, and include fever, headache, muscle aches and pains, headaches, weakness and exhaustion. The distinct nature of these symptoms sets influenza apart from other respiratory viruses which may be ‘flu-like’, but aren’t actually THE flu, such as the viruses which cause the common cold. When someone has the flu virus, they are infectious (i.e. they can transmit the virus to others) for 1-2 days before symptom onset until 5-7 days after (1). The virus is very easily spread, which can be directly via droplets from a person coughing/sneezing/talking which enter the nose/mouth of another person, or indirectly such as via someone touching a surface contaminated by these droplets. Symptoms of the flu generally last about one week, but it varies from person to person (2). The severity of the illness predominantly depends on individual risk factors (see below), the flu strain the person has and whether they are vaccinated against influenza or not.
There are four main types of influenza virus – A, B, C and D, and the first 3 of that list are those which can cause disease in humans (1). We mostly see influenza A and B causing illness every year during flu season, and within those subtypes, there are different strains of influenza A and B. Oh, science – it’s rarely simple! The influenza virus is pretty smart, so it undergoes minor genetic changes quite frequently, and far less commonly can undergo major changes, resulting in a new virus sub-type. For this reason, the World Health Organisation monitors influenza around the globe throughout the year, and uses these insights to give us recommendations for what strains of influenza virus should be included in our seasonal influenza vaccine, based on what strains their data shows are circulating. This year (2019), the vaccine being given in Ireland and the U.K. is a ‘quadrivalent’ vaccine, meaning it protects against FOUR strains of influenza – two A strains, and two B strains (1,3).
Who should have the influenza vaccine?
Certain groups of the population are recommended to have the seasonal influenza vaccine every year. These are (3,4):
- Those aged 65 and older
- Pregnant women
- Adults and children (over the age of 6 months) with certain chronic long-term health conditions*
- Healthcare workers
- Carers (both formal and informal)
- Residents of long-term stay residential care homes or other long-term stay facilities
- Persons working in close contact with poultry, pigs and/or water fowl
*Please read a full list of these conditions on the National Health Service (NHS) website here 3 for those in the U.K. and on the Health Service Executive (HSE) website here 4 for those in the Republic of Ireland.
In Ireland and the U.K., the flu protection given is very slightly different. In Ireland, an injected influenza vaccine is used for adults and children aged 6 months and older (4). In the U.K., children aged between 6 months and 2 years are offered an injected flu vaccine, while those aged between 2 and 17 years of age will usually be offered the flu vaccine nasal spray (3,5). You can read more about these age specifications for those in the U.K. on the NHS website here for adults (3) and here for children (5).
Vaccination is a health topic which has been unfairly subject to a lot of misinformation that has been propagated online, especially via social media. It’s really, really important that those who are recommended to get the season influenza vaccine do so, as this preventive measure helps reduce the overall number of cases of influenza, the spread of illness and disease severity (including the number of hospitalised patients and patient deaths due to the flu) (1).
So, let’s look at three common myths about the seasonal influenza vaccine, and bust them!
Myth #1: The influenza vaccine can give a person the flu.
BUSTED. The virus strains used to make the seasonal influenza vaccine are inactivated (i.e. killed) during the vaccine manufacturing process, so the ‘dead’ virus in the vaccine literally CANNOT give a person the flu.
The vaccine causes the body to mount an immune response against virus, and this process, where the body makes antibodies to fight the flu virus, takes approximately two weeks to be fully effective (1). Sometimes, people may catch the flu virus in that two-week period between getting their flu shot and it being fully effective – or, they may catch another respiratory virus which isn’t the influenza virus. Either of these possibilities may lead the person to think that they became unwell and ‘got the flu’ because of the flu vaccine, but we know that this isn’t true.
The potential side effects of getting the vaccine are also quite minor in comparison to the potential illness burden due to flu itself. Local reactions on the skin after receiving the injected flu vaccine such as redness and/or minor swelling are the most common vaccine side effects (but please note, these do not affect the majority vaccinated), followed by less commonly more general symptoms lasting 1-2 days such as muscle aches, mild fever and/or headaches (these general symptoms represent the body mounting an immune response to the flu, which is a good thing!) (1). Anaphylactic reactions to the injected vaccine or its constituents are very rare, occurring at a rate of less than one in one million (1). There are very few contraindications to the vaccine, which you’ll find listed here (6) for the based in the U.K., and here (4) for those based in Ireland.
Myth #2: Healthy people can’t get the flu.
BUSTED. Anyone can contract the flu and become unwell. It is absolutely true that certain groups of the population are more likely to get the flu (and its potential complications) than others as we’ve said above. However, healthy people can catch influenza, and some can have quite severe disease as a result of it.
Healthy people can also of course spread influenza virus. This is especially important in the context of healthcare workers and carers, as they spend their working days looking after sick and vulnerable patients – so by getting their flu shot, they are minimising their own risk of becoming unwell due to the flu, and most importantly, the big risk of spreading the flu virus to patients they look after, many of which are at increased risk of more severe disease due to influenza.
If you’re a healthcare worker or carer reading this, please be sure to speak to your employer or GP regarding getting the seasonal influenza vaccine as early in the flu season as possible – and if you know someone working in these occupations, give this article to read!
Myth #3: The seasonal influenza vaccine doesn’t work.
BUSTED. Okay, let’s discuss.
The seasonal influenza vaccine does work – very well. It has been used for more than 60 years around the world, with rigorous safety monitoring throughout that time. It is effective at reducing the number of influenza cases, and the burden of disease due to influenza (i.e. hospitalisations, intensive care admissions and deaths for example) (1). The vaccine is less effective in older persons and those with chronic health conditions, simply because their immune systems aren’t as strong, so they mount a less effective immune response.
However, the research tells us that they SHOULD definitely still be vaccinated, as vaccination still massively reduces their chances of getting influenza and its possible complications (1). Plus, as we’ve said, the vaccine takes approximately two weeks to be fully effective, which is why it’s really important to get vaccinated as early in the flu season as possible (i.e. October!)
Finally, the effectiveness of the vaccine also depends on the match between the viral strains the vaccine protects against, and the viral strains which circulate during flu season. As we’ve already said, the flu virus is pretty sneaky, so it can genetically change quite a bit (which is why the WHO monitors it so closely) – but more often than not these changes are minor and don’t affect the overall effectiveness of the vaccine. And remember, this season’s vaccine protects against FOUR strains of influenza virus, with just one shot! The protection given against the flu by the vaccine lasts approximately one year (4), which is why the at-risk groups mentioned above are advised to get vaccinated at the start of each yearly flu season (i.e. October).
Remember, vaccines work, and vaccines save lives – so this flu season, get the vaccine, not the flu!
(1) Health Protection Surveillance Centre (2019) ‘Health care workers & seasonal influenza vaccine: 2019 – 2020 influenza season.’ Available at: https://www.hse.ie/eng/health/immunisation/hcpinfo/fluinfo/flupresentation.pdf
(2) National Health Service (2019) ‘Flu.’ Available at: https://www.nhs.uk/conditions/flu/
(3) National Health Service (2019) ‘Flu vaccine overview.’ Available at:
(4) Health Service Executive (2019) ‘Flu vaccine.’ Available at:
(5) National Health Service (2019) ‘Children’s flu vaccine overview.’ Available at: https://www.nhs.uk/conditions/vaccinations/child-flu-vaccine/
(6) National Health Service (2019) ‘Who should not have the flu vaccine?’ Available at: https://www.nhs.uk/conditions/vaccinations/who-shouldnt-have-flu-vaccine/