Will the Influenza Vaccine Make You Sick?

Whether you choose to get it or not, being informed is a good thing

Virology Blog

There are a lot of myths floating around the influenza vaccine, and it’s always better to make choices related to your health that are based on facts rather than myths. One of the common myths is that the vaccine will give you the flu, so that’s the focus of this post.

Vaccine basics

When an infectious agent enters the body, its goal is to start replicating and making more of itself. Your immune system wants to shut that down. There are several layers to the immune response, and a key element is the production of antibodies. These are Y-shaped proteins your body makes that are specific to that infectious agent. They latch onto it and sort of wrestle it to the ground so that other components of the immune system can go to town.

The body is very good at remembering antibodies it has already made. The next time it’s exposed to the exact same infectious agent, antibodies can be produced quickly so they can take care of the infectious agent before it makes you sick.

Vaccines expose you to a part of the infectious agent so your body can produce antibodies before you’re exposed to the infectious agent itself.

There are two broad groups of vaccines: one is live attenuated (weakened virus that is still capable of replicating) and the other is inactivated (the virus is unable to replicate).

The influenza vaccine

The diagram above shows an influenza virus. The squiggly bits in the middle are the viral DNA, which is what gets you sick. That’s contained within a capsule, which has various proteins sticking out of it (the purple and gold coloured bits).

The injectable flu vaccine contains proteins that are found on the outside of a flu virus, specifically forms of hemagglutinin (H) and neuraminidase (N).

There’s no viral DNA contained in the vaccine, and the DNA is what makes you sick, so the injectable flu vaccine can’t possibly give you the flu. There’s simply no biological mechanism for this to happen.

The nasal spray formulation of the flu vaccine is different. It contains live weakened virus. It’s not going to make people with a healthy immune system sick, but people who are immunocompromised or on immunosuppressant medications can get sick, so it’s generally recommended that they avoid live vaccines.

What’s good and what’s not about the influenza vaccine

Let’s start with the bad.

Influenza is not a stable virus. It mutates a lot, and the predominant strains change from year to year.

You may recall hearing about the H1N1 flu or other letter/number combinations. The H and the N correspond to the hemagglutinin and the neuraminidase protein that the flu virus attacks. The numbers refer to different variants of these proteins. The World Health Organization predicts the most common strains for the upcoming flu season, and vaccines are developed to target those H and N types.

The problem is, the flu virus doesn’t necessarily do what the WHO predicts it’s going to do. As a result, you may not end up covered for all the flu strains you might be exposed to in a given year. This means the flu vaccine is a lot less effective overall than other vaccines for more stable infectious agents, and you may end up getting sick with the flu from a strain of the virus that’s not covered by the vaccine.

Now it’s time for the good.

Those immunocompromised people who shouldn’t take the live virus nasal spray vaccine? If they catch the flu, it could actually kill them.

Same with the elderly. People with chronic respiratory conditions can also have significant complications from the flu. These are the people that need protecting, and that’s why getting vaccinated is important.

If you catch the flu, you’re already infectious the day before you start to feel sick. Say you’re going to visit your grandparent in a care home. You unwittingly spread your germs all over the place. People get seriously sick. Not good, right?

As a nurse, I’m required to get a flu shot, not for my own protection, but for the protection of my patients that I could pass my germs to.

If you’re not coming into contact with people who are at high risk of complications from the flu, it’s probably not that important to get the vaccine. Then again, the more people who get vaccinated the safer it’s likely to be for at-risk people.

What if you get sick after the vaccine?

One option is that when your body is generating the immune response that it’s supposed to, you may feel a little under the weather. This isn’t an infection, it’s your body doing its thing.

Another option is that you were exposed to a strain of flu virus that wasn’t covered by the vaccine, and the timing just happened to coincide with when you got the flu vaccine.

It’s also possible that you got a cold. While colds and the flu are both respiratory infections, they are completely different viruses. That means the flu vaccine gives you zero coverage for colds. The flu causes achiness all over, extremely low energy, and a significant fever. If you don’t have a fever, chances are you’ve got yourself a cold.

On a related note, the term “stomach flu” is a misnomer. Influenza is a respiratory virus that doesn’t affect the gut. “Stomach flu” can be caused by a variety of infectious viral or bacterial agents, none of which are influenza.

Well, there you have it. It’s up to you whether you get the flu vaccine or not, and there may not be a strong reason for you to get it, but informed choices are always better than choices based on myths.

Originally published at https://mentalhealthathome.org on November 7, 2019.

Mental health blogger | Former MH nurse | Living with depression | Author of 3 books, latest is Managing the Depression Puzzle | mentalhealthathome.org