This photo of a syringe is strikingly similar to the actual influenza vaccine injection that I experienced. [Image credit: eddmun via stock.xchng]
I hate needles. Which is why I have steadfastly refused to get the flu shot. I’ve categorized it as an extraneous injection, reserved for the elderly or masochistic. That is, until this year’s flu season.
In September, I was struck with the world’s worst cold. The NYU Health Center told me there was nothing I could do, except rest and drink plenty of fluids. And to come back in a few weeks to voluntarily shove a needle filled with flu virus deep into my skin.
It got me thinking: Why are my doctors always telling me to get a flu shot? What does it do inside my body, anyway?
Here’s what I knew about vaccines before I started researching the subject: Someone sticks you with a needle, you make antibodies, and — voilà! — you don’t get sick.
And that’s where Carol Reiss, a biologist at New York University and editor-in-chief of the journal DNA and Cell Biology, came in to school me on all things immunological.
Reiss explains that when someone becomes infected with the flu, the virus begins to replicate inside the cells in the air sacs in the lungs, the alveoli. Then, if everything is working properly, your body’s immune system fights off the virus by using memory T-cells to kill the virus.
“In about a week or two you will have, circulating in your body, lots of antibody that was made against that virus,” says Reiss. “And also memory t-cells that, when re-exposed to virally infected cells, kill them.”
Furthermore, once you’ve had the virus that is circulating, you become immune to it and you will never get that specific flu again.
The flu shot always contains three dead strains of flu that the U.S. Centers for Disease Control and Prevention and the World Health Organization have identified as the most common strains of flu that could affect the target area during the upcoming flu season, said Reiss. So the shots may change every year and may differ for different places.
The flu viruses in the vaccine always include an H1, H3 and B strain, which are different versions of the common flu. The H3 strain is a type of influenza A, while the H1 strain is a seasonal influenza A (like H1N1, or the swine flu).
Each strain includes two proteins: hemagglutinin, which binds the flu virus to the cell it wants to infect, and neuraminidase, an enzyme that enables the virus to easily transmit itself.
The purpose of the flu shot is to induce your body to develop antibodies to these two proteins, decreasing the virus’ ability to enter your cells.
The small changes in the flu over time, known as antigenic drift, would not affect a person who had already had a seasonal flu. But if antigenic shift, or a sudden change, occurs it could cause a flu pandemic, which is when the flu spreads rapidly around the world. Even if you’ve had last year’s virus, you’re still likely to get the flu if infected by a pandemic strain.
When your body detects an antigen, like the particles of flu virus in the vaccine, T-cells, the infection-fighting white blood cells, go into action. They immediately alert B-cells, different white blood cells, to create antibodies to the specific virus they have detected.
It’s like that time you tried to get into a nightclub, but were wearing jeans. In the case of the flu, antibodies are like your lung’s dress code: They identify virus particles as antigens and make sure the bouncers, the T-cells, work to remove them.
There is one more very important factor you should remember about the relationship between people and the flu shot: Most people have been sick before.
This matters, Reiss explains, because of something called “original antigenic sin.” That is, if a person has been previously exposed to a virus, and assuming they have a healthy immune system, they already have antibodies that their memory B-cells have produced. So the flu shot only enhances the antibodies we already have, and do a “really lousy” job inducing new antibodies to the new seasonal variants, says Reiss.
A better alternative, Reiss suggests, is flu nasal-spray, called FluMist, which is made from live-attenuated, cold-adapted virus (meaning the virus used in the vaccine is both weakened and temperature-specific). The flu mist is a more effective vaccine, she says, because it sprays live-viruses directly into your nose, as opposed to the flu shot, which goes in the arm. Reiss says that flu mist causes increased immunity, because it creates “mucosal immunity,” as opposed to the flu shot, which “…will give you antibodies in your big toe, [but] the infection’s in your lungs.”
However, because the nasal spray contains a live virus, it is not recommended for everyone, especially those with weak immune systems who could be considered ‘immunocompromised’. The CDC recommends that the following groups of people do not receive the nasal vaccine: people who are too young or too old (younger than 23 months or older than 50), young children with asthma, pregnant women, those with long-term health issues like heart disease or anemia, those with nerve or muscle disease, those with compromised immune systems or those who are in close contact with someone who has a compromised immune system, and children and adolescents on long-term aspirin treatments. Also, because the vaccine is grown in chick embryos, those with egg allergies are cautioned against receiving the vaccine.
Sometimes with the nasal spray there is a mild symptom of stuffiness, because the virus from the mist is replicating in your nose and your body is responding to it, says Reiss. But the nasal spray can work in small children and even people with HIV.
For us needle-phobic folks, the flu mist could be our savior.
(And in case you’re wondering, I was too busy running far, far away from the needle-filled Health Center to remember to tweet after I got my shot.)