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Updated 8/30/2021

The Danger of Flu

The CDC estimates that about 8% of the population gets the flu every year--about 38 million people were affected in the 2019-2020 flu season and about 22,000 deaths. It can affect the young and healthy as well as those with other medical conditions. The flu is highly contagious, making it hard to avoid if one of your family members brings it home. I have personally seen the effects of a heavy flu season. I started my medical career in 2009 and witnessed first hand the scary effects of the swine flu epidemic which affected over 59 million Americans.



The chart below shows that the flu vaccination reduces the risk of flu illness by between 19% and 60%. The 2019-2020 estimated efficacy was 39%. In general, current flu vaccines tend to work better against influenza B and influenza A (H1N1) viruses and offer lower protection against influenza A (H3N2) viruses.

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When to Get Immunized

We recommend getting vaccinated in September or October. There is also evidence that immunity from prior year’s shot can linger to subsequent years. Remember that it takes about two weeks for immunity to develop after receiving the shot.


We have chosen to use the quadrivalent (four flu strains) preparation Flucelvax because it provides broader coverage for influenza B strains. This one is also grown by cell culture, not in eggs, giving it the potential to be more effective and safer. We use the adjuvanted preparation, Fluad, for patients over 65 years-old as it has shown better efficacy in this age group. This has an added ingredient which stimulates a better immune response without using higher doses of vaccine (but is not egg free). We only use preservative-free, single-dose vaccine preparations.

Precautions to Consider

Egg allergy used to be a reason to avoid the flu shot, but not anymore. It is shown to be safe in this group, with very unlikely reactions occurring. Regardless, we use egg-free preparation for people up to age 65 due to better efficacy, so there’s no possibility of reaction.

The one reason to avoid the shot is a history of Guillain-Barré Syndrome (a severe paralyzing illness, also called GBS). The connection between the flu shot and GBS is not completely certain, but it is quite compelling (best estimate is 1-2 cases per million flu shots given). If you have had this, we don’t want to give you the vaccine, although that recommendation does not come from the CDC. It is just our personal practice. We also avoid giving the vaccine if you are currently ill with a fever.


Vaccinations are always a personal choice, but we strongly support use of the flu vaccine to provide whatever protection possible against the flu. Epidemics in our history have caused major suffering and death, and we have a way to reduce our risk--even if a 30-60% reduction seems small. Side-effects from the shot are possible, but very rare.

More Questions?

For more information, refer to the CDC website, which contains the most unbiased information available now and updated information on flu activity. You can also review the Arizona Department of Health, where they monitor current flu data.