The Flu shot explained
FYI – I had my flu shot a month ago. I have for the last 25 years. I have not had the flu in that time(touch wood). Used to get the flu yearly before that.
Experts: If You Don’t Get A Flu Shot, You’re Stupid. And A Dick
Asheville, NC: I finally got my flu shot yesterday, and in my post-vaccination low-grade fever haze, I was reminded how much misinformation exists about flu shots.
But this dispatch isn’t about how much I hate the anti-vaccine movement and how the triumph of public health has led to masses of pampered, scientifically illiterate hippies believing the kind of stuff that makes homeopathy look sane by comparison. No, this is about the nitty gritty of seasonal influenza vaccinations. Give me your tired, your poor, your huddled masses yearning to breathe free: let us speak of flu!
First things first: influenza is an asshole. It hates you and wants to shred the lining of your lungs, turning you into its own private incubator of nasty, drowning you in a froth of dead cells, bodily fluids, and the refuse of your own immune response. In your average year, the flu will kill 250,000 to 500,000 people worldwide. However, in an above average year, flu can be a mass killer. For example, the Spanish Flu pandemic of 1918 killed between 20 and 50 million people. And that was before airplanes. So yes, in case you were wondering, you should definitely care about flu.
Flu belongs to the Orthomyxoviridae (Greek for straight mucus viruses) family of RNA viruses, which contains the three genera of Influenzavirus: Influenzavirus A, which infects humans, birds, and other mammals; Influenzavirus B, which infects humans and seals; and Influenzavirus C, which infects humans and pigs. All of them suck. Some of them suck more than others.
Influenza A viruses are the culprits in all flu pandemics, and are thus a very big deal, so let’s take a closer look. You’re probably somewhat familiar with the subtype (or serotype) nomenclature, for example H1N1 or H3N8. But here’s what those letters and numbers actually mean…
The classification of Influenza A viruses is based on two viral surface proteins: hemagglutinin (HA or H) and neuraminidase (NA or N). Influenza hemagglutinin is a glycoprotein with antigenic properties: antigens are substances that can trigger the production of one or more antibodies, so for the purpose of this explainer, you can just think of antigen as a synonym for “bad guy”.
Influenza hemagglutinin is the thing that is responsible for binding the virus to the cell that is it trying to infect. Without this viral surface protein to bind sialic acid on the cell membranes in your upper respiratory tract, the Big Bad Flu would just float around in your lungs doing diddly squat. Hemagglutinin is the flu glue that allows the viral particles to stick to a healthy cell, then grapple-hook its way inside, entering the cell in a bubble, or vesicle, of the cell’s own membrane. By entering the cell instead of fusing with the cell, influenza evades the immune system, hiding in the very place it’s going to hijack for its own reproduction.
Next: viral neuraminidase, which is what allows the influenza virus to be released from its cozy host cell, post-replication. Once the virus has gotten busy inside the cell, hijacking the cellular machinery to make copies of itself, it needs a way to bust out all the freshly minted virions. This is where neuraminidase comes in. Neuraminidase makes it possible for the virus to be released from the cell by cleaving an important group, the sialic acids, thus allowing brand new baby flu virions to float free until their hemagglutinin surface proteins find a sticky, healthy lung cell to hook into and start the entire thing all over again. Without neuraminidase, the new virons that burst forth could get stuck to the sialic acid in the dead cell’s membrane, ruining their dreams to replicate inside of and destroy a new host cell. No neuraminidase, no escape.
Here’s where it gets nasty: Sixteen hemagglutinin subtypes and nine neuraminidase subtypes have been identified for influenza A viruses. Not only that, but out of all the parts of an influenza virus that change, or mutate, the hemagglutinin and neuraminidase surface proteins do it the fastest. This little rapidly mutating surface protein thing is pretty unique to influenza: Other viruses can mutate, but it’s typically not their surface proteins that change. This is why you can’t get the measles twice: your body knows measles’ surface proteins and recognizes them every time measles shows up. Influenza, on the other hand, changes its surface proteins all the fucking time, making it hard for your immune system to recognize and destroy.
The myriad influenza serotypes like to hang out in different combinations, like a particularly grotesque swingers party. To use the nomenclature, swine flu, or H1N1, has hemagglutinin serotype 1 and neuraminidase serotype 1. So, when someone starts talking about “strains of flu”, these specific combinations of HA and NA surface proteins are usually what they are referencing.
Which brings me to flu shots. Obviously, influenza viruses are complicated little assholes. With so many combinations of surface proteins, researchers have to decide which strains to put in each year’s seasonal flu vaccine. They do this by monitoring strains of influenza in circulation and making – yes you guessed it – supremely educated guesses. Most years the strains of flu in the vaccine closely match the flu strains in circulation. And when the match is good, the vaccine is incredibly effective.
Your immune system, elegant bastard that it is, can recognize virus particles via its immune receptors, little do-dads that are tailor-made to identify and bind to the antigens on the virus’ surface. It’d be kind of like having an incredibly specific home security system, except that instead of just calling the cops whenever trouble showed up, your house would remember intruders and deploy a counterattack system uniquely suited to the exact nature of the disturbance. So, if there was a very tall man that kept trying to break into your house, your house would learn that each time he showed up all it had to do was quickly drop the ceilings a foot or two to knock him out.
However, in the case of this metaphor, influenza is a collective of burglars with varying skill sets. Sometimes influenza is SAS, sometimes it’s the Navy, sometimes it’s a bunch of punk kids with flaming bags of shit. Your house, unable to protect against every burglar in this weird super villain group hell-bent on stealing your flat screen, must hedge its bets and prepare for the burglars it thinks are most likely to show up. Which is essentially what the scientists developing each year’s seasonal flu vaccine do. Researchers predict which viruses to include in the vaccine, and despite the fact that flu viruses are constantly changing, a phenomenon called “antigenic drift”, they are usually able to predict pretty close matches between viruses in the vaccine and the circulating viruses. Impressive.
Each year’s flu vaccine is trivalent, meaning they protect against three influenza viruses. This season’s vaccine is made from an H1N1 and H3N2-like strains of influenza A, as well as a strain of influenza B. And before you get all huffy because you got a flu shot last year with H1N1 in it, know that the H3N2 and influenza B strains are different from those in last year’s vaccine. So you still need this year’s flu shot.
But Leigh, I’m a healthy adult that never gets sick! Why on earth would I let a stranger jab me with a needle and deposit killed, inactivated viral particles in my perfectly toned deltoid?
Well, I’m glad you asked. As Dr. Zubin Damania (or as you may know him, ZDoggMD) reminds us in his charmingly bizarre video, One Injection: The Flu Shot, up to half of people with documented influenza viral infection are asymptomatic. These lucky bastards get the flu but don’t experience any symptoms, then spread the flu to the vulnerable populations who will definitely experience symptoms. So even though that asshole yapping on Bluetooth, spraying spittle all over the cream and sugar counter at your neighborhood chain coffee shop may seem physically robust, he could in theory be spreading flu to vulnerable members of the community, like little kids and old people. “These folks should get immunized,” notes Dr. Damania in our email correspondence, “Or else they are dicks.”
Per the CDC, everyone six months of age and older should get vaccinated for seasonal influenza, especially those at high risk of developing serious flu-related complications. According to Dr. Damania, those most at-risk for developing flu-related complications include the very young, the very old, those with immune system problems like HIV and cancer patients, and sufferers of other chronic diseases such as diabetes, COPD, and CHF.
However he is careful to note that during the H1N1 outbreak, they saw “young, healthy people dying all over the place from the flu.” So everyone should get immunized, unless they have a severe chicken or egg allergy, have had a severe reaction to an influenza vaccine, or a history of Guillain-Barré Syndrome, or are under six months of age. These unlucky folks can’t get immunized and will just have to hope that everyone else gets a flu shot, giving them a chance to cash in on some community immunity.
(Community immunity, also referred to as herd immunity, is a fantastic perk that can result from mass vaccination. Says Dr. Damania: “When everyone that can be immunized is immunized, the virus really has nowhere to hang out, so the more vulnerable members of society (very young, very old) for whom vaccines are less effective due to weaker immune response, etc. are protected by proxy.” However, current seasonal flu vaccination rates are too low to confer this fantastic and life-saving benefit.)
Still not convinced that flu shots work? Dr. Damania has some friendly advice. “Take an adult education class on basic biology. Then take another class on basic statistics. Then review the literature on flu vaccine efficacy (particularly Japanese studies), and the data showing benefit. Now, since I know nobody is actually going to go through all that trouble, outsource the education/research to someone who does this for a living (a doctor, epidemiologist, immunologist, the CDC, etc) and listen to their recommendations.”
And no, you absolutely cannot get the flu from a flu shot. You might have to suffer through a low-grade fever, headache, or body aches, but that’s just your immune system ramping up and making some priceless influenza antibodies. However, I’m sure that enterprising readers can milk some sympathy courtesies out of their weenie, post-vaccine state. I know I sure did.
See Desknotes for the complete interview with Dr. Zubin Damania.