With all of the recent talk about COVID vaccines, we don’t want to forget about flu season and the importance of also getting your annual flu vaccine to stay protected. One major point of confusion that we often see relates to the difference between the various vaccines. Which one should I get? What does quadrivalent mean, and what about trivalent? When should I get the high dose and what makes it so special? In this article we will work to clear up some confusion about the flu shot and answer some questions about who should get what and when.

To make this simpler, let’s back up and talk about the flu itself a little bit. The flu, or “influenza,” is a virus that has quite a few different strains. They all make you feel about the same (sick), but all are a little bit different. A good way to visualize this is think about a dog. There are different kinds of dog breeds, but at the end of the day they are all a dog- they all bark, they all run around and do essentially the same thing even though they look different. This is the same for the different strains of flu virus. Each year, the U.S. Food and Drug Administration (FDA), Centers for Disease Control (CDC), World Health Organization (WHO) and other health experts meet to analyze data and predict what the most common strains of flu virus will be for the upcoming influenza season. This information is what the vaccines are based off of every year to get the safest and most effective vaccine out to the public!

Standard dose vaccines

Starting with the standard dose vaccines, you have probably heard people talk about getting the quadrivalent (quad) or trivalent (tri) flu vaccine. This year (2022-2023 season) there will be no trivalent vaccine available, meaning that all vaccines will be quadrivalent. Quadrivalent means that the vaccine provides coverage for 4 different strains of the flu virus. Trivalent meant that there was coverage for only 3 strains.

What is a high dose and when do I need to get it?

You may have heard people talking about something called the high dose flu vaccine (HD), which may lead you to wonder, “Do I need that one instead of the standard dose?” The main qualifier for needing the HD vaccine is age. The HD vaccine is meant for people that are 65 and older; in fact, the Advisory Committee on Immunization Practices (ACIP) recommends that all people over 65 should get the high dose version.

Why do older people need the high dose vaccine?

According to the CDC, people that are 65 years and older have a higher risk for flu-related complications, illness, hospitalization and even death. The idea is that using vaccines that may potentially be more effective for this older group of people can help to avoid some of these serious outcomes.

The CDC also states that 70-85% of flu-related deaths occur in people 65 years of age and older. The high dose vaccine contains 4x the amount of antigen as compared to the standard vaccine. An antigen is a substance that, once injected, triggers an immune response and the production of antibodies to help your body build up protection. The HD is also “adjuvanted,” meaning that it has an ingredient that helps create a stronger immune response. People over the age of 65 still CAN get the other flu vaccines if they desire, but as previously mentioned, the ACIP recommends that they get the HD version.

This table gives a summary of all flu vaccines for the 2022-23 season:

Now that we have learned a little bit about who gets what vaccine and what is out there, we will go into some common concerns, questions, and myths that you may hear about the flu vaccine.

A common thing people will say is that the flu vaccine is going to give them the flu anyway, so why should they bother to get it?

I can assure you it is impossible to get the flu from receiving the vaccine. With the exception of FluMist, all of the other vaccines available are inactivated. This means that the viruses are killed (inactive) before you receive them. Since the virus is dead and cannot spontaneously come back to life, there is no way that it can make you sick. It simply shows your immune system what the virus looks like, so if you do happen to become exposed, your body already knows what to do and can fight it.

FluMist does contain the live virus, but it is attenuated, meaning weakened, so that it cannot cause illness. It should be noted that since FluMist is live, it should not be given to people who are pregnant or immunocompromised, among some others.

If it can’t give me the flu, then why do I still feel sick after receiving the vaccine?

It is completely normal to feel “sick” after receiving the flu vaccine (or any other vaccine for that matter) because your immune system is responding! This is actually a good thing; it means your immune system is working, recognizing the vaccine, and learning how to fight and ultimately “kill” it. Some normal side effects that you might notice are soreness at the injection site, headache, low grade fever, tiredness and general body aches. These are completely normal and safe side effects that will go away much faster than having the flu itself. Some people don’t have any of these side effects, and that is normal too!

Can I still get the flu after being vaccinated?

You may hear people talking about how the flu shot does not work or that they still get the flu after being vaccinated. Sometimes they are not completely wrong. Even after getting the flu shot, it is still possible to get the flu. If this happens, your symptoms and duration of being sick are usually much less and you will have a lower chance of developing severe symptoms or being hospitalized. The efficacy of the flu vaccine does vary each year depending how well scientists match up the flu strains of what is predicted versus actual. Remember- these are developed almost a year ahead of time!

What about the recombinant thing?

Flublok is the recombinant flu vaccine, and this one is a little different than the others. This vaccine was approved by the FDA in 2013, and is the only vaccine that is completely egg free. These is the perfect option for people that may have a severe egg allergy!

Now that I know which vaccine I need, when should I receive it?

In the U.S., flu season happens in the fall/winter, with its peak being between December and February. This being said, flu activity can last as late as May. Since it takes ~2 weeks for your immune system to build immunity after vaccination, it is recommended to take this in consideration when deciding when to get vaccinated. For optimal protection, we aim to schedule our flu clinics in late-September through October.

Finally, the big question- is this vaccine safe for me to get and also give to my child…?

Thankfully, the answer is YES! – anyone who is 6 months of age or older should receive the flu vaccine annually.

All of the current flu vaccines are approved by the FDA, and they are meticulously tested for both being effective and being safe! There has been extensive research done on these vaccines, and over the past 70+ years, hundreds of millions of people have safely been vaccinated.

Fun fact: 1945 was the year that the first flu vaccines were approved for the general U.S. population!

In conclusion, it is a good idea to get vaccinated against the flu this year and every year. The flu has been overshadowed by COVID recently, but this doesn’t make the flu any less significant. The flu causes severe sicknesses and deaths every year, between 20,000-51,000 deaths per year actually! The vaccines are safe, effective and widely available – your local pharmacy, hospital clinics, urgent care, doctor’s offices, and even many places of business have vaccination days. The best news is that a lot of times the vaccine is free under your health insurance and the process is usually quick and easy!

Written by: Matthew Ruvinov, PharmD Candidate 2023

Edited by: Megan Holland, PharmD and Danielle Chamness, PharmD

Here is a timeline looking back on past flu pandemics and vaccine history:

https://www.mayoclinic.org/coronavirus-covid-19/history-disease-outbreaks-vaccine-timeline/flu#:~:text=get%20flu%20vaccines.-,1945,t%20in%20the%20U.S.%20military.

For any questions or concerns, remember that your local pharmacist is a great resource to utilize! You can also find more detailed information online, some helpful sources are linked below:

• https://www.cdc.gov/flu/about/index.html
• https://www.cdc.gov/flu/prevent/flushot.htm
• https://www.fda.gov/vaccines-blood-biologics/lot-release/seasonal-information-influenza-virus-vaccine
• https://www.cdc.gov/flu/spotlights/2021-2022/specific-vaccines-seniors.htm
• https://www.cdc.gov/flu/about/season/flu-season.htm

Read about other vaccine recommendations here.