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By Joe Alton, M.D. aka Dr. Bones and Amy Alton, A.R.N.P., aka Nurse Amy
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Why Are Flu Vaccines Sometimes Ineffective?

Tuesday, January 2, 2018 16:44
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Why Are Flu Vaccines Sometimes Ineffective?

flu vaccine

flu vaccine

The Centers for Disease Control and Prevention (CDC) are reporting that 36 states are in the midst of widespread influenza outbreaks. It appears that this flu season might be a bad one, but why? And will the usual vaccines be effective in preventing you for getting the flu this winter?

You might think that, okay, I got the vaccine, so I can’t get the flu this winter. You might be surprised to know, however, that the CDC shoots for about 40-60% vaccine effectiveness in preventing the illness, not the 100% you expected. In fact, last year’s vaccine was 42% successful (less against H3N2), on the low end of the CDC’s target, but in 2014-2015, the prevention rate from the flu vaccine was about 19%.

(Note: This is neither an anti-vaccine nor pro-vaccine article. It is simply a discussion as to why influenza vaccines seem to be less effective in preventing disease in recent years.)

Influenza vaccines produced in a particular year are derived from certain proteins found in last year’s virus. The CDC makes a determination about what virus they expect to be dominant in the coming year, and companies base their production on those predictions. If you have the material from last-year’s flu, why are vaccines sometimes so ineffective in achieving their purpose? Mainly because of two concepts we’ll discuss today: Antigenic Drift and Antigenic Shift.

Antigenic Drift: Viruses are notorious for their ability to mutate, but fortunately their mutations rarely make a major change in their genetic makeup. When the changes are so small that the current virus going around is essentially the same as the previous one, it is called antigenic drift. In this circumstance, vaccines are more effective; that is, they reach the CDC goal of 40-60% prevention rate because they are fighting essentially the same virus.

mutations caused Ebola to be transmissible from bats to humans in West Africa

mutations caused Ebola to be transmissible from bats to humans in West Africa

Antigenic Shift: Sometimes, a virus undergoes a major mutation or two viruses combine to make a significant change in the nature of a virus. For example: If the Ebola virus primarily lives in fruit bats in Africa, some mutation along the way made it able to live in human beings. Perhaps another mutation made it more easily passed along to other humans in bodily secretions. These significant changes in the genetic makeup are called antigenic shifts. With antigenic shifts, all bets are off with regards to predicting the success of a vaccine in preventing disease. To take an extreme example, if the Ebola virus mutated to make it easily transmissible via airborne droplets, we’d be in a lot of trouble.

Classifying Influenza Viruses

The dominant virus causing this year’s influenza cases in the H3N2 Type A virus. Influenza viruses are classified according to the proteins that exist on their surface. These are called Hemagglutinins (HA) and Neuraminidases (NA). There are more and more different HA and NA subtypes discovered every year. The Swine flu, for example, is H1 N1.

Why is flu vaccine less effective against influenza A(H3N2) viruses?

The journal Proceedings of the National Academy of Sciences suggests that last year’s vaccine’s ineffectiveness occurred as a result of an antigenic shift in the H3N2 virus. Indeed, the flu vaccine seems to be generally less effective against influenza A(H3N2) that other viruses. Why? This from the CDC:

“While all influenza viruses undergo frequent genetic changes, the changes that have occurred in influenza A(H3N2) viruses have more frequently resulted in differences between the virus components of the flu vaccine and circulating influenza viruses (i.e., antigenic change) compared with influenza A(H1N1) and influenza B viruses. That means that between the time when the composition of the flu vaccine is recommended and the flu vaccine is delivered, H3N2 viruses are more likely than H1N1 or influenza B viruses to have changed in ways that could impact how well the flu vaccine works.”

In other words, H3N2 tends to develop mutations more often and faster than other common influenza viruses.

The CDC goes on to say: “Growth in eggs is part of the production process for most seasonal flu vaccines. While all influenza viruses undergo changes when they are grown in eggs, changes in influenza A(H3N2) viruses tend to be more likely to result in antigenic changes compared with changes in other influenza viruses. These so-called “egg-adapted changes” are present in vaccine viruses recommended for use in vaccine production and may reduce their potential effectiveness against circulating influenza viruses.”

Therefore, the flu vaccine as currently produced is less effective in its purpose than we would like. More research is necessary to produce a vaccine that we can depend on to prevent the disease, and to make it safer for those opting to take it.



In the meantime, ask your physician for an anti-viral med (not an antibiotic!) that may decrease the duration and severity of the disease, such as oseltamivir (Tamiflu) or zanamivir (Relenza). As these drugs are more effective in the first 48 hours of symptoms, you should have these on hand, just in case your doctor isn’t able to see you quickly. I recently received an official CDC health advisory emphasizing the increased importance this year of these medications due to the issues related to the H3N2 virus. It also stated that early treatment may decrease the risk of hospitalization.

Joe Alton MD

Dr. Alton

Dr. Alton

Find out more about influenza and 150 other medical topics in the award-winning Third Edition of “The Survival Medicine Handbook: The Essential Guide for When Medical Help is Not on the Way”


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Total 2 comments
  • Takealook

    Vaccines are designed to injure so why would they be effective against a disease?
    They are not of course any more than fluoride being forced into our water supply
    is helping with dental health.

  • gracer

    This is how I have managed to stay well since the winter of 2015. I have recently posted this comment under various articles about colds and flu.
    My method is to not get a sore throat, chest cold or flu in the first place, thanks to quercetin dihydrate. Quercetin is found in apples, onions and many other fruits and vegetables.
    The following two supplements keep my lungs and sinuses healthy and my lung and sinus mucus thinned and liquefied.

    What works for me is taking the yellow powder, quercetin dihydrate. It somehow galvanizes my lungs and sinuses.
    I am someone who believes that 500 mg per day (mornings) of quercetin dihydrate powder (about a level half measuring teaspoon) is enough to guard the lungs and sinuses and protect them from colds and flu. I haven’t had my normal winter chest cold since starting quercetin 3 years ago.
    I thought that quercetin wasn’t helping me at all, so to discontinue taking quercetin I twice dropped the dose to either 250 mg or zero (nothing), but both times I had the sniffles within a month. So it takes at least 400 mg of quercetin per day for me. I also realized that quercetin had been giving me energy so I was glad to restart taking it.

    I buy quercetin dihydrate in the 250 gram bag at Bulk Supplements. A 250 gram bag will theoretically last about 500 days at 500 mg per day.

    For thinning and liquefying lung and sinus mucus, for decades I have taken a level half teaspoon of Mrs. Dash Table Blend (MDTB) seasoning mornings. It seems to take about 2 weeks to start thinning lung mucus so it can be coughed up more easily. The sinuses probably take longer to clear but should eventually. Increasing the MDTB dose doesn’t seem to increase the results.
    I just put both the Mrs. Dash Table Blend and quercetin in mouth together and wash down with water. It’s quicker that way.

    The more exact dose of Mrs. Dash table Blend that I have taken for decades with great results in thinning/liquefying lung and sinus mucus is 1/2 level measuring teaspoon mornings. I now just use a 7 inch long stainless steel iced teaspoon (1 level iced tsp) because it dips way down into the deep seasoning container easier.
    I had laryngitis in the Fall of 2016 where I couldn’t clear my throat, even though I was taking 500 mg of the aforementioned quercetin. I restarted taking the Mrs. Dash Table Blend and my throat cleared the same day, so there is something in this 14 herb seasoning that thins mucus, maybe the lemon oil.
    I eat dairy and cheese, but dairy in general and increasing dairy intake also seems to increase mucus production for me for a day or two.

    I buy MDTB at Walmart in the 6.75 oz size which lasts over 3 months.

    My take on vitamin C is that it doesn’t keep me from taking colds and flu. The same with vitamin D-3.
    I took lots of vit C for years during the 80′s and 90′s. I would take it up to bowel tolerance.
    I took vit D-3 at 5000 units/day for 5 years starting in 2011 because I read that D-3 protects the lungs from getting colds and flu but I still got a chest cold each winter.
    Quercetin is what prevents colds and flu for me and I would try quercetin for any lung or sinus problem.

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