Flu Vaccines — Which One is Right for You?

Betty Chaffee/ October 30, 2019/ immunization, vaccines/ 6 comments

Hopefully, most of you have already had your flu vaccination for 2019/2020. But the realist in me knows that lots of us put it off til "later", and a some of us never get around to it at all. So, the likelihood is that a good number of readers haven't yet gotten vaccinated against influenza this season.

I'm not here to convince you that getting a flu vaccine is one of the best ways to keep from getting the flu and its consequences. Alan Tanabe did a great job of making that case in his recent article during National Immunization Awareness MonthThis follow-up article assumes you have decided to get immunized and are wondering which of the many available formulations is right for you. We'll go through some FAQ's about immunizations, and if your burning question isn't answered, leave a comment at the end and we'll get to it ASAP.

What's the difference between Inactivated Influenza Vaccine and Live, Attenuated Influenza Vaccine?

All influenza vaccines contain proteins (called antigens) that cause our body to mount an immune response. The antigens are either pieces of inactivated virus, or live virus particles that have been weakened (attenuated) so they can't actually cause the flu. In both cases, the particles look just like the flu virus to the immune system. The body produces proteins to fight off this invader, and for the next several months, if the real flu virus attacks us those proteins will fight it off to keep us from getting sick.

Most available flu vaccines are inactivated. The virus particles aren't capable of producing illness, so almost anyone can be safely vaccinated with this type of vaccine. Inactivated flu vaccine is what you get when you're given a "flu shot".


The only live, attenuated vaccine is a nasal mist. It's approved by the FDA for use in people between the ages of 2 and 49. It's great for kids (and adults) who are frightened by needles, especially those who would otherwise not get vaccinated. Be aware, though, that it's a live influenza virus. Attenuating the virus means that it's been weakened, so it won't cause illness in people with a healthy immune system. But those with weak immune systems could become ill with influenza if they are given this type of vaccine. Anyone who has a weak immune system (from organ transplants, medications for certain diseases) should NOT be vaccinated with live, attenuated flu vaccine. Not only that, but if you are a healthy person living with or caring for someone with a weak immune system, the live virus vaccine is not for you.

What's the Difference Between "Trivalent" and "Quadrivalent" Flu Vaccine?

All influenza vaccines are manufactured to be effective against more than one strain of influenza. Some are made to work against two strains of Influenza A and one strain of Influenza B. These are called "trivalent" vaccines. Others are made to work against two strains of each type of Influenza, and are called "quadrivalent" vaccines. Though it makes sense that covering for more strains of flu would provide better protection, research hasn't clearly shown that. You can ask about a quadrivalent vaccine, but if it's not in stock get vaccinated with the trivalent product. It's safer than waiting.

What is "High-dose" Flu Vaccine?

High-dose flu vaccines contain about four times as much antigen as the standard-dose vaccines. They are approved by the FDA for use in people 65 years of age and older. We've known for a long time that as we get older, our immune systems just don't kick in the way they used to, so it's tougher to mount an adequate antibody response to vaccines. The idea behind the high-dose vaccines is that by giving a higher dose of the inactivated virus particles, the body will be more likely to produce a response.

And that might be true, but we don't have adequate research yet to firmly answer the question. Some information points to improved responses, including fewer hospitalizations and emergency visits, with the high-dose product. But there's not enough information from large groups of people to say for sure. And keep in mind that the injection-site and systemic side effects seem somewhat more common with the high-dose product. For now, the recommendation for those age 65 and up is to ask about the high high-dose product. But if it's not in stock, get vaccinated with the age-appropriate product available.

What is "Adjuvanted" Flu Vaccine?

Adjuvanted flu vaccines were marketed to tackle the problem of weaker immune response in the elderly. We talked about how high-dose vaccines do this earlier. Instead of using a higher dose, adjuvanted vaccines have an added  ingredient that helps improve the immune response. This type of flu vaccine is also approved for use in those age 65 and up.

Is it really better? Well, the data aren't all that clear. There has been research indicating that there's no difference in immune response between the standard vaccine and the adjuvanted vaccine. But then there's been research that points to a better immune response with the adjuvanted product. For now, the recommendation is that it's reasonable for those at 65 and up to ask for the adjuvanted vaccine. But if it's not available, vaccination should take place with any age-appropriate flu vaccine.

What about people who are allergic to eggs?

The amount of egg protein in flu vaccines is extremely low. We now know that the benefit of immunization far outweighs the very small risk of an allergic reaction. For those with egg allergy, including stomach discomfort or nausea, rash, and hives, vaccination with any age-appropriate product is recommended. If you have a more severe egg allergy, you should still get vaccinated, but it's best to do it at your doctor's office where they can watch you for 15-30 minutes afterward.

If you haven't gotten your flu vaccine yet, do it soon!

Protect yourself and your loved ones from the flu and its complications. Go to your local pharmacy today! If you have other questions about vaccination, ask your community pharmacist, or contact us at BetterMyMeds!



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About Betty Chaffee

Betty Chaffee, PharmD, is owner and sole proprietor of BetterMyMeds, a Medication Management service devoted to helping people get the maximum benefit from their medications.


  1. Wow! Thanks for explaining the different types of vaccines. I haven’t had a flu shot in years. I stopped after getting sick, right after getting the shot and that was two years in a row.
    One question that I have is “Are small amounts of mercury, as a preservative, used in flu vaccines?”

    1. Good question, Tony. For the most part, thimerosal (a preservative that contains mercury) has been removed from vaccines. Even though there’s no good evidence that thimerosal causes problems, FDA is doing its best to take the ingredient out of all vaccines because of the fear it has caused in the past. The only influenza vaccines that contain small amounts of thimerosal are those that are sold as multiple-dose vials. A large majority of flu vaccines are given from single-dose vials or syringes, and they don’t contain thimerosal. If your immunizer is giving you a vaccine from a single-dose product, you can be confident it doesn’t contain thimerosal.

      And, to the other point you made, influenza vaccines can cause side effects in some people, including headache, fever, nausea, and muscle aches. They sort of mimic flu symptoms, but they’re usually mild and go away in a couple of days. Since the flu shot contains inactivated virus particles it doesn’t cause people to come down with influenza. People are safer getting vaccinated to prevent actual influenza, which can be debilitating and even life-threatening. Hoping you’ll change your mind this year!

  2. Thanks for explaining the different types of flu vaccine. I received the high dose vaccine because of my age and also because I have Crohns disease.

    1. That’s great, Marie, and thanks for your comment. I’m glad you were able to find the high-dose vaccine – not everyone stocks it.

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