Should I get the flu vaccine? And if so, which one? The Influenza vaccine, winter 2024-2025 edition

How do we know that the winter is coming?

Simple – when we start hearing about the flu shot. So, lets get started with the flu talk, 2024-2025 edition!

How can we predict the strain of influenza viruses that will be arriving next winter?

If you got to this link after having read the general chapter about the influenza virus, then you probably know by now that the influenza viruses can have many different strains.
Each year, the world health organization monitors mortality and the types of strains that are found in the southern hemisphere, which is where the flu arrives before it reaches the northern hemisphere and before it reaches all those people that prepare the vaccine.

Is there a way to prevent ourselves from getting the flu?

Yes. There is a vaccine.
The seasonal influenza vaccine is administered at the beginning of the winter season. The contents of the vaccine vary from year to year, depending on the decisions made by the World Health Organization, who base their choices on data collected from the southern hemisphere.
For the 2024-2025 season, there will be several different vaccines available in North America but all of them are anticipated to be trivalent. More information will become available at a later time.

I recall that last year there were quadrivalent vaccines available. Why has it changed this year?

You are right, last year both the live attenuated vaccine and the inactivated vaccine contained 4 different components.
However, this year the influenza B/Yamagata vaccine component in the flu shot is being removed because this component has not been detected after March 2020. So the WHO and FDA recommended to remove this component from the vaccines until 2024-2025.

What are the names of the viral strains in this year’s flu vaccine?

The composition of the vaccines for flu season 2024-2025, as per the decision of the World Health Organization, is as follows:
• A/H1N1
• A/H3N2
• B/Austria strain

Does it really matter whether I get the trivalent or quadrivalent flu shot?

The answer to this is no.
Keep in mind that there are certain differences between the available flu shots out there but the difference does not lie in the number of variants in the shot. This does not have much significance.

Why do we need to get the flu vaccine every year?

This is because we have yet to invent a universal shot that would be suitable for all the different strains out there and would provide long-term immunity.

Who should get vaccinated? Who can get vaccinated?

Inactivated vaccine – theoretically anyone over the age of 6 months and younger than 120 years. The high-dose inactivated vaccine is available only for people over the age of 65.
Live-attenuated (nasal) – anyone between the age of 2 and 50 years is eligible for this vaccine. Please note the comments about this below. Apart from age, there are other contraindications for this vaccine.

Who cannot receive the inactivated vaccine?

• Up until last years, people with egg allergy were advised to receive the vaccine at a medical institution that could provide them with adequate care in case they developed an allergic reaction to the shot. However, this year’s guidelines permit people with egg allergy to get their shot anywhere.
• People who have previously experienced a severe allergic reaction to the shot cannot receive it again.
• People (adults or children) who are experiencing a medium-severe acute febrile-illness are advised to wait until they have recovered before receiving the vaccine. I would like to expand on this point because I often hear parents saying they avoided the vaccine because their child had a runny nose without fever. When you postpone receiving the shot because of a simple cold you may eventually end up missing the entire flu season. Sometimes, children are sick with a runny nose throughout the entire winter season and so I strongly recommend you postpone the shot only if your child has a febrile illness.
• A precaution is set for those who developed Guillain-Barre syndrome 6 weeks following a previous flu shot.
All other people over the age of 6 months can receive the shot. Immune-suppressed people can also receive the shot. The immune reaction to the vaccine may not be as good in people with immune-deficiency/suppression but we do not have a way to “quantify” this reaction and this is not a reason to avoid the vaccine.

Who cannot receive the live-attenuated flu vaccine (intranasal)?

• Children under the age of 2 years or adults over the age of 50 years
• Pregnant women
• People who experienced a severe allergic reaction following a previous flu shot
• People with a congenital or acquired immune-deficiency, or with a suspected immune deficiency.
• An episode of wheezing in the 3 days prior to the shot, having received steroids by mouth or having been hospitalized at an intensive care unit due to asthma exacerbation. People who regularly receive steroids by nasal route can receive the vaccine, regardless of the dose.
• Children between the ages 2-18 years that receive medications that belong to the salicylate family (for example: aspirin) for a long period of time
• People at any kind of medical state that poses them at risk for aspiration or that are unable to handle secretions due to a respiratory or spinal cord disorder, etc.
• People with a cerebrospinal fluid leak or people with a cochlear implant
• People (adults or children) that have a febrile or non-febrile acute illness that is medium to severe in intensity, including people with severe nasal congestion – it is preferable to wait for recovery before getting the vaccine.
• People who received antiviral medications in the two days prior to their vaccine appointment. Such antiviral medications are not recommended also in the two weeks following the administration of a live-attenuated vaccine as they may have an effect on the efficacy of the vaccine.
• Precautions are set for the following:
– Severe nasal congestion or a medium to severe disease with or without fever. I recommend waiting till recovery.
– People who developed Guillain-Barre syndrome 6 weeks following a previous flu vaccine.
– People who are at high risk of developing severe complications as a result of influenza infection including people with chronic respiratory illness (not including asthma), cardiovascular disease, kidney/liver disease, neurological illness, hematological or metabolic illnesses including diabetes.
In short one could say that the live-attenuated vaccine is advised only for people who are generally healthy and are between the ages 2-50 years
This is super important! Anyone who received the live-attenuated vaccine should avoid contact with people who have severe immune deficiency or suppression in the week following its administration.

Is there an association between the COVID-19 vaccine and the flu shot?

No. Both vaccines are recommended this year.

What are the possible side-effects of the inactivated flu shot?

The most common side effect is a local reaction to the shot, that is: tenderness that may last 24-48 hours. Other side effects include mild fever, muscle pain, cough, etc. – can last 24-48 hours.
I have heard about people who could have sworn they caught the flu after getting the shot. It is possible that the virus was incubating in their bodies before they received the vaccine but most of the time it is simply a misunderstanding of what the real flu is.
The inactivated flu shot cannot cause illness and cannot cause you to catch the flu, it’s as simple as that.

What are the side effects of the live-attenuated vaccine?

The most common side effects include runny nose, nasal congestion, nasal bleeding and throat pain – these can last 1-3 days. Systemic side-effects include fever, headache, muscle pain, abdominal pain and more – these are less common but can also last for 1-3 days following the vaccine.

How can babies under the age of 6 months get the flu vaccine?

Infants under the age of 6 months cannot get the flu vaccine, but you can protect them from the flu by doing the following:
• Exclusive or partial breastfeeding from a mother who received the flu shot passively transfers antibodies to the baby. Breastfeeding mothers can receive either type of flu vaccine.
• Vaccinating all other family members – so that the virus does not ‘enter your home’.

Are there different types of vaccines available for different populations?

In many countries, the live-attenuated vaccine is recommended for children aged 2-18 (unless they have any reason not to receive this vaccine).
Does this mean that the live-attenuated vaccine is better than the other vaccine? Absolutely not. It is probably because of the ease at which the live-attenuated vaccine can be administered.

What about adults over the age of 65?

In most countries a high dose seasonal influenza vaccine is available for adults over the age of 65. Nonetheless, the local side effects for this vaccine are higher than the regular-dose vaccine.

Who (do I think) must get the flu vaccine?

In my opinion, everyone has to get the vaccine. I mean, why not?
There are always certain populations for whom the vaccine is more strongly recommended, because of their higher risk to develop severe flu illness. But I really think everyone should get it.

How many doses of flu vaccine should we receive?

For people over the age of 9, a single dose is required.
Children under the age of 9 who have previously received 2 doses of flu vaccine (in a single season or in multiple seasons), only require a single dose.
Children under the age of 9 who have never been vaccinated for the flu or who have received a single dose in the past, are eligible for 2 doses that must be administered 4 weeks apart.
When a child receives a second dose of flu vaccine it is preferable to administer both vaccines from the same manufacturer and with the same composition. However, if a second dose from the same manufacturer is not available, then whatever is available should be used.

Where is the flu vaccine administered?

The inactivated vaccines are given intramuscularly in the thigh or arm, depending on the age of the person receiving it.
The live-attenuated vaccine is given as a nasal spray in the nose.

Can we minimize the pain felt when the flu shot (or any other shot) is given?

Absolutely!
As mentioned already in previous posts, we can minimize the pain felt in any vaccine by distracting the child who is receiving it.
The age at which this method of distraction works, depends on the child and his parents, their character and the patience of the person administering the vaccine.
I use a technique called “the cough trick”. I ask the child to look away and cough 7 times (or 10, or 13, whatever I feel like at that particular moment).
When the child is calm and cooperative, I administer the vaccine together with one of his coughs and many times the child does not feel the pain.
This technique can be used for any of the routine vaccines, after a certain age when the children are cooperative. It also works on adults that don’t like vaccines…

Can the flu vaccine be given together with other vaccines?

Inactivated vaccine – in general, this can be administered together with any other vaccine In some countries, it is advised to wait 3 days between the influenza vaccine and the meningococcus B vaccine in children under the age of 1. You can read more about the meningococcus vaccine here.
Live-attenuated vaccine – this can be administered together with any other vaccine, including other live-attenuated vaccines. If you cannot receive the other live-attenuated vaccines on the same day, it is advised to wait 4 weeks before receiving other live-attenuated vaccines (for example – the measles/mumps/rubella with or without varicella vaccine).
When it comes to COVID-19 vaccine, you can receive it on the same day or any time before or after the flu shot, there are no restrictions.

How effective is the flu vaccine?

Efficacy is a major drawback when it comes to the flu vaccine.
The vaccine does not always correctly predict the strain of flu for the upcoming season, due to the many different existing strains that change from year to year and it is possible that to begin with the influenza vaccine is just not as efficacious.
Just as an example, we know that its efficacy in preventing disease in all the different age-groups in North America was only 47% in 2018-2019 season.
There are age groups where the efficacy was higher (children between 6 months to 1.5 years had 61% efficacy) and lower (adults over the age of 50 had only 24% efficacy).
So, why even bother with this vaccine in the first place? Why get vaccinated when the efficacy is clearly insufficient?
a. Efficacy varies from year to year, there are years that it has been as high as 70%.
b. Those who get vaccinated and still catch the flu experience a milder illness than those who are unvaccinated.

And therefore, the main reason I would say for why we should still get the flu vaccine is because we have no other means of protecting ourselves from the illness. If I were to suggest you get only 50% of quite an unpleasant illness, that has the potential to lead to complications, I think you would take the offer.

I am hopeful that in the future someone will invent a universal vaccine that will cover all the different strains, one that we are able to receive as a single dose, once in our life.

In summary, there are families that come back at the end of the flu season to thank me for vaccinating them at the beginning of the season because they did not catch a cold that season. That’s great, but I always tell them that it’s a matter of luck. The flu vaccine decreases the chances of getting the flu but does not affect your chances of getting any of the other viral illnesses that circulate during the winter season.
There are people who I have vaccinated in my own hands, that have caught the flu. It is frustrating. Fortunately, in most of the cases the illness is minor and milder than what it would have been, had they not received the vaccine.
And back to our main concern here and that would be children: because children are at a higher risk of catching the flu and developing a more severe disease, I think that is our responsibility, as parents, to make sure they receive their flu vaccine, every flu season. This applies to healthy children, as well.
On a personal level, I will tell you that I will get the flu vaccine this year and will vaccinate all three of my children myself, as I do every year.
I hope you all do the same.