Should I Get the Flu Shot?

Many of my patients are asking me if they should get a flu shot. Even those who typically have not sought the vaccine every year are now curious as to what to do.

This influenza season is unprecedented in that it will coincide with the continued, or recirculating SARS-CoV-2 (which causes the disease COVID -19). As a respiratory virus, these symptoms may be confused with influenza. Also, it is possible to get both viruses at the same time and during the same season.

Not to mention, we have seen the effects of COVID-19 overburden our hospital system and workers. Getting vaccinated with the flu shot could potentially decrease the stress on the system, allowing for those patients who are sickest to be able to get the care they need. Imagine needing a hospital bed for yourself or a loved one, or worse a ventilator, but they are all occupied.

What is the flu?

The seasonal flu, or “flu”, or influenza, is a serious virus that claims thousands of lives each year and hospitalizes many more. A typical US influenza season runs from late fall to early spring, usually peaking in January or February.

When discussing the flu and its impact, it is imperative to differentiate influenza from other little nuisance viruses. I call them “little nuisance viruses” because although they may cause some illness and burden on the system, including lost days at work, they don’t generally kill people (unless something else is going on).

You see, many people use the word “flu” to describe any number of viruses. One example of this is the “stomach flu”. The stomach flu (medical term: gastroenteritis) is actually not the flu at all. It is caused by a completely different virus.

Influenza is not the “stomach flu”. And although influenza can cause symptoms of nausea, vomiting, and diarrhea, it is not to be mistaken for gastroenteritis. Most gastroenteritis is caused by an infection from a self-limited virus and lasts approximately 1-5 days. Influenza, on the other hand, is a potentially deadly respiratory virus.

Additionally, there are a host of other viruses that cause an influenza-like illness, or “ILI”. These include the virus that causes the common cold.

Chances are, if you have had the actual flu before, you know it. You say things like “I felt like I was going to die”, “I felt like I wanted to die”, or “I couldn’t get out of bed for a week”.

Now that that is cleared up, when I refer to the flu here, I am referring to influenza. And the flu vaccine is directed towards the serious respiratory virus.

Am I at greater risk for serious complications from the flu?

Those at increased risk from flu complications are older adults (65 +), infants and very young children, pregnant women, and people with certain medical conditions like heart disease, cancer and diabetes.

What are the symptoms of the flu?

The most common symptoms of the flu are:

  • high fever and chills
  • intense muscle aches
  • fatigue
  • headache
  • cough
  • sore throat
  • runny or stuffy nose.

How do I prevent the flu?

Like COVID-19, the spread of flu can be minimized by social distancing, quarantining when ill, using face coverings, and good handwashing practices.

Influenza vaccine can prevent influenza (flu).

What is a vaccine?

A vaccine is something that has been developed to produce an immune response from your body. This immune response includes the formation of antibodies, which are like little soldiers that can specifically identify and protect against the specific disease for which they were created. Therefore, if you come into contact with or contract the actual virus, your body will be “primed” and ready to fight the infection.

What kinds of vaccines are there?

There are several different ways to make vaccines. A “live attenuated” vaccine is made by growing the virus over and over in a culture of cells until it is a weakened version of the original. Because this is still technically a live virus vaccine, live attenuated vaccines should not be used in certain people with weakened immune systems. Again, if you think this is you, discuss it with your physician.

One of the most commonly offered flu vaccines is the “inactivated” vaccine. Inactivated, or “killed”, virus vaccines are inactivated by using heat or chemicals. This produces a less strong response which also usually doesn’t last as long- one of the reasons why the influenza vaccine is sometimes recommended to be given twice during the season for certain populations.

Finally, there are subunit/conjugate vaccines. These vaccines are developed against a specific part of the pathogen (disease-causing organism). For example, one of the vaccines for COVID-19 is directed against its ‘spike protein’ (a specific part of the Sars CoV-2 virus).

Who should get the flu vaccine?

The CDC recommends everyone 6 months of age and older get vaccinated every flu season.

Why should I get a flu vaccine?

An important point as to why we vaccinate for the flu is because of its potentially deadly nature. You see, vaccines and vaccine programs are expensive to develop. They require a lot of research and resources. And chances are, they have side effects, as their entire purpose is to mount an immune response from the host (YOU). So why would a vaccine with potential side effects, that requires a lot of resources be developed and recommended for so many? Because it can save lives. And not just yours, but the people around you (via a concept called “herd immunity”).

For example, we don’t have a vaccine for the common cold, frequently caused by the rhinovirus, because it is a self-limited disease that does not usually cause serious sequelae (complications). On the other hand, influenza can cause a number of complications, such as bronchitis, sinus infections, ear infections, and pneumonia.

So how does influenza contribute to causing these other infections? Similar to COVID-19, the flu has a large inflammatory “cascade” that it causes in the body, which can be the main source of serious morbidity and mortality. It can cause a lot of “secondary infection”. Secondary infection is usually a bacterial infection that happens as a result of the immune system being “kicked when it’s down” (or in this case, “kicked when it’s busy”).

Does everyone get the same kind of flu vaccine?

Different types of vaccines are indicated for different groups of people.

The inactivated (killed) recombinant vaccine is indicated for most people.

There are two newer high-dose inactivated quadrivalent vaccines, Fluzone® and Fluad®, indicated for ages 65 or greater. These vaccines contain 4x the dose of the standard flu shot.

Otherwise, according to the CDC, none is better than another (manufacturer-wise).

Live-attenuated virus vaccines should not be given to people without a functioning spleen, cerebrospinal fluid leak, or cochlear implant, as well as the other precautions for people with suppressed immune systems. Speak with your physician.

Because viruses are grown in eggs, there has been some concern over whether or not persons with an egg allergy can receive the vaccine. The CDC and AICP recommendations state that for persons with severe egg allergy this may be an issue. There are some egg-free vaccines available as well. Again, talk with your physician.

How effective is the flu shot?

The answer to this question is “it depends”. It depends on how old you are (older age is less effective with the lower dose vaccine), your baseline state of health (basically how functional your immune system is), the type of vaccine given, and how similar the circulating viruses are to what’s in this year’s vaccine.

Let me dive into that last point. There are different types of Influenza (A and B). These can be broken down further into subtypes (Influenza A) and lineages (Influenza B). During any given flu season, there can be several types – and subtypes/lineages- of virus circulating. And guess what! These viruses are tricky. They may shift their composition even during the season.

Every season’s vaccine is determined based on scientific study of seasons past, and scientists’ best guess of what strains might be around this year. As you might imagine, this is not the easiest thing to predict, given the shifting of the strains of influenza virus, along with the large number of other viruses (ILI’s) out there, and the number of people who actually got tested for the flu. Add to that the effectiveness of each test and how good it is at detecting actual disease, which is affected by such things as the characteristics of the test itself, and how good the provider is at getting the sample. This all adds up to a mighty task for epidemiologists!

The early 2020 influenza season (February-March) saw a higher percentage of Influenza B.

This season’s inactivated vaccine is a quadrivalent vaccine, meaning it is updated to include 2 Influenza A subtypes (H1N1 and H3N2) and 2 Influenza B lineages. According to the CDC, even if the subtypes and lineages don’t match exactly, it may still provide some protection against this season’s flu.

Some studies show the immunity to Influenza A (H3N2) wanes more quickly than the other types, showing somewhere between 54-67% effectiveness. This may not seem like much but is pretty darned good if an intervention is going to prevent every 1 out of 2 people from getting the virus!

Every time I get the flu vaccine, I get the flu.

I hear this a lot. However, this is highly unlikely. You may feel like you have a mild version of the flu, because your body’s immune system is getting its soldiers “at the ready”, which basically means it is being primed for when it actually sees the influenza virus. It is quite normal to feel some mild symptoms of the flu after a flu shot. There may also be some tenderness or redness at the site of the vaccination. Additionally, there are all the other viruses (see above “What is the flu?”) running around as well, and in particular this season, there’s COVID-19.

For a minority of people, it is also possible to get sick, or have a flare of their chronic autoimmune disease, after their immune system has been challenged at all (in this case with a vaccine). If you are, or think you may be, in this category, it is important to discuss the vaccine with your physician prior to making the decision of whether or not to vaccinate. As an integrative physician who cares for a lot of people with autoimmune disease, a percentage of my patients fall in this category. In this case, shared decision making is paramount.

The flu shot never works for me.

As described earlier, there are a host of other viruses that can make you sick during the season that are not the flu.

Additionally, during the flu season, it is possible to get the flu if a different strain than what is included in the vaccine is circulating, or if your immunity to the flu wanes over the course of the season (see above “How effective is the flu shot?”).

I decided the flu vaccine is right for me. So now when should I get it?

If the decision is made to get the influenza vaccine, it is recommended that it be given by the end of October 2020. This is due to the unpredictable start of the influenza season, and the possibility that immunity from the vaccine may wane over the season. Once received it will take about 2 weeks for immunity to develop. Parents of young children under 8 years should discuss timing with their pediatrician as they will likely need two doses. There is currently no recommendation for revaccination if a person age 8 or older has already had a vaccine this season.

I have already had a flu shot this year. Do I need to get another one?

It’s important to note that “this year” does not equal “this season”. Early 2020 is a different flu season than late 2020.

If I am sick can I get a vaccine?

If you are sick with a minor cold, then you can still be vaccinated. However, if you have fever or are otherwise moderately or severely ill, you should wait until your immune system is done fighting that infection first. Speak with your physician if you are unsure.

Are there any drugs that can treat the flu?

Yes, there are medications, called antivirals, that can be used to treat the flu. However, these medications are only effective if they are given very early in the course of the disease, and they are not without side effects. Additionally, there can be shortages of drugs available to treat the flu.

Are antibiotics effective against the flu?

No. Influenza is caused by a virus. In fact, most respiratory infections in the normal host with a normal immune system are viruses. Antibiotics, which are used to treat bacterial infections, are ineffective against viruses.

References

CDC and the CDC’s Advisory Committee on Immunization Practices (ACIP) 

For more information, visit www.cdc.gov/flu.

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