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00:00Will this hurt?
00:05I mean, I know it'll hurt a bit, but like, how much?
00:10Why does a flu shot have to come in a needle anyway?
00:13Why can't it be like a cookie or a muffin or something?
00:20Dear Cassie and Moby, why do we have to get flu shots every year?
00:25Big fan, Ellie.
00:27Hi, Ellie.
00:29Flu shots protect us from this little bugger, the influenza virus.
00:33It's what causes the flu and all the coughing, body aches, tiredness, and fever that come
00:39with it.
00:40It's not usually a huge deal for healthy people.
00:43We feel sick and then we feel better.
00:46But for others, especially older folks, the flu can be serious or even deadly.
00:53Flu shots help us fight off the virus before it can make us sick and before we can spread
00:59it to others.
01:01Unfortunately, the flu virus is a tricky one.
01:05It's always coming back in new disguises.
01:08So this year's flu shot won't protect us from next year's flu.
01:14That's why scientists and doctors all over the world constantly track the viral villain
01:19to predict where and how it'll pop up next and stay one step ahead.
01:27All viruses have one goal, to replicate or make more copies of themselves.
01:33But they can't do it on their own.
01:35They have to get inside our bodies.
01:38Then they infect or invade our cells, taking them over and turning them into little virus
01:45factories.
01:47One infected cell can produce thousands of viral copies.
01:52Influenza targets cells inside the nose, throat, and lungs.
01:56So when a person with the flu sneezes or coughs, they can spew out thousands of copies of the
02:02virus.
02:04Anyone who inhales them can get sick.
02:07That's what makes the flu so contagious or easy to spread.
02:11During colder months, it's even worse.
02:14First, everyone's hanging out indoors more.
02:17And the air is a lot drier, which means droplets and coughs and sneezes can stay afloat longer.
02:23That's why that time of the year is known as flu season, when many people get sick all
02:29at once.
02:32Fighting off the infection is the job of our immune system.
02:36It's a network of cells, tissues, and organs that are on 24-hour alert for any invaders.
02:43See those spikes on the flu virus?
02:45The immune system uses them to identify it as an intruder and build antibodies, a substance
02:52that sticks to that specific germ.
02:55Depending on the kind of antibody, this can disable or destroy the germ, or market for
03:01destruction by other immune cells.
03:05It takes a while for your immune system to build brand new antibodies for a germ it's
03:10never seen before.
03:12That's why the flu usually lasts a week or so.
03:16Now imagine if we already had the antibodies in time for flu season.
03:21That's what flu shots do.
03:24They're vaccines.
03:25They jumpstart the process of making antibodies by showing our immune system what to attack.
03:32Flu shots use dead or severely weakened viruses to do that.
03:36They're powerless and won't get us sick.
03:39But your immune system recognizes them as a threat and starts building antibodies.
03:45Then if the real deal comes along, your body will destroy it before it can get you sick.
03:52Antibodies last for years, so we usually don't get sick from the same bug twice.
03:58See, the flu virus is constantly shape-shifting because of its genetic code.
04:05Those are the instructions on how to replicate.
04:09Influenza is a sloppy virus.
04:11Its genetic code is prone to mistakes called mutations.
04:15These can lead to changes in those outer spikes.
04:19And if they no longer match perfectly, the old antibodies can't detect them.
04:25Our immune system has to learn to battle the new type or strain of flu from scratch.
04:32And while our bodies are figuring it out, the virus has time to replicate and spread
04:37to new victims.
04:39So every year, scientists around the world race to get ahead of this process.
04:45They identify which flu strains are on the loose and report them to organizations like
04:51the World Health Organization or WHO.
04:55The info is used to develop a flu shot that's effective against the strains you're most
05:00likely to catch that year.
05:02It's not 100% effective.
05:05There are way more influenza strains going around than they can put into a single shot.
05:10But each year, the flu vaccine prevents millions of illnesses and thousands of deaths.
05:16Oh!
05:17Flu muffins!
05:18You did it!
05:25Huh.