Disclaimer
Standard disclaimers apply. I’m not a scientist. This is not a text book. I have opinions. You’re free to ignore them.
How Vaccines Work
While vaccines work in different ways, they all have the same end result- they teach your body how to fight viruses. The human body is an amazing machine with an astounding ability for self-protection and repair that we call the Immune System. Vaccines work by teaching antibodies (the seek-and-destroy part of your Immune System) what a particular virus looks like. Once your body has the blueprint of a virus in place, it can figure out how to destroy said virus in a variety of ways. What’s more, once your body has a template in place, it remembers for the rest of your life (…ish) how to beat that virus, and keeps the antibody template on-hand forever (…ish).
Types of Vaccines
Inactivated vaccines:
Inactivated vaccines are, simply put, dead viruses. Scientists isolate a virus, “kill it” (there’s some question as to whether viruses actually qualify as being “alive,” but we’re going to say they are), and then inject it into your body. Your body sees the foreign invader, builds an antibody template for it, then destroys it. Since the virus was already dead before it was ever injected, it can’t hurt you. (You can’t get the flu from a flu shot!!!!) However, your body’s pull-no-punches attack on the dead virus can cause you to feel pretty bad- fever, chills, body aches, etc.
Much of what makes you “feel sick” isn’t the virus/bacteria/fungus that’s invading your body, but your body’s response to it. You get a fever because most bacteria and viruses are very temperature-sensitive: raise the temperature, kill the invader. Anybody who’s ever said, “Every time I get the flu shot, I get the flu.” is really referring to their own body’s immune response to the vaccine. This (usually very short-lived) period of feeling less than well is the price your body is paying for long-lasting (…ish) immunity to a virus.
These vaccines often don’t have to be refrigerated, travel well, and have a long shelf life. If you’ve ever had a flu, polio, or rabies shot, you’ve probably been injected with an inactivated virus.
Live-attenuated vaccines:
Live-attenuated vaccines vaccines are only “mostly dead” when they’re injected into your body. Since they are live viruses, they allow your body to produce a better blueprint and create a longer-lasting immune response: often providing life-long immunity (no ish this time) with only a couple of injections, but since they are live pathogens, they’re not recommended for anyone with a compromised immune system.
If you’ve been vaccinated for measles, mumps, or chicken pox, you’ve been injected with a live-attenuated virus. Since the virus has to be kept alive up until your body squashes it like the bug it is, these vaccines have to be kept refrigerated and don’t travel all that well.
Sub-unit and Recombinant Vaccines:
Sub-unit and Recombinant Vaccines (also known as polysaccharide, and conjugate vaccines) are created when scientists isolate one or more pieces of a virus (a specific protein, or a particular carbohydrate) and use it to teach your body what to attack. In these cases, what is injected into your body is not a virus (dead or alive), but a unique piece of that virus.
Think of these like gang tattoos- you don’t have it identify individual gang members; you just have to know that anyone with that tattoo is in a rival gang. The body sees the tattoo and knows that someone doesn’t belong.
These are completely safe for anyone, because there’s no “payload” in them- no virus; nothing that can make you sick. Again, as with any vaccine, your body’s own immune response might make you feel crummy for a little while, but it’s not the vaccine making you sick. If you’ve been vaccinated against pneumonia, meningitis, HPV, or shingles, you’ve had a sub-unit type of vaccine
DNA, RNA, and mRNA Vaccines:
This class of vaccine is still largely experimental, but is very much the future of immunotherapy. These techniques use the fundamental building blocks of a virus to “reprogram” human cells to fight against them. I know…sounds spooky, right? But, that’s really what all the other methods above do- they use all or part of a virus to tell your body how to fight it. DNA and RNA vaccines skip the middle man and change the DNA of the virus, or the person directly.
Ish:
Remember all those ishes above? When talking about anything as complicated as the human body, it’s almost impossible to make any sort of blanket statements. Different people respond differently to vaccinations, and some don’t get as long-lasting effects as others. Also, viruses are tricky beasts and some of them mutate very quickly.
The reason you need to get a flu shot every year is that this year’s flu isn’t exactly the same as last year’s flu.
The reason you don’t always get the flu, even if you don’t get a flu shot is that it’s still a flu.
Some people (maybe most?) can retain enough flu immunity year to year to be able to fight off a slightly mutated version of it, but some can’t. You can never be sure when the flu mutates just enough for your body not to recognize it anymore, so an annual “booster” keeps your body primed to fight off the flu in its many forms.
The COVID-19 Vaccine
Currently there are two COVID-19 vaccines available in the U.S. One from Moderna, and another from Pfizer. They’re both mRNA vaccines. Wait, didn’t I just say that mRNA vaccines are experimental and spooky? Yes, I kind of did, but experimental doesn’t mean untested and spooky doesn’t mean dangerous. Anything we don’t understand can be spooky, and pretty much none of us understand virology.
The COVID-19 vaccines were developed in early 2020, and spent a year undergoing rigorous testing before they were approved for general distribution. mRNA vaccines may be the cutting edge of science, but that doesn’t mean they aren’t safe.
How the COVID-19 Vaccines Work
mRNA
mRNA (literally Messenger RNA) are little bits of ribonucleic acid that serve as the bike messengers of the construction company that is DNA. These messengers send blueprints to the manufacturing centers in your cells and say “Boss says start making this.” Your cells look at the blueprints and say “Sure, I can do that.” and then shifts the entire manufacturing capacity of that cell into making the thing. It could be a protein, or a sugar, or more RNA or DNA strands. It could even be fully-formed and functional viruses (see our previous discussion on how viruses work). Basically, whatever the mRNA says to build, the cell builds.
Signature Protein
As we discussed before, viruses are bits of DNA wrapped in (usually) protein. Cells ingest the protein and then the DNA goes to work. COVID-19 has one particular bit of protein wrapped around it that human cells find absolutely scrumptious. Cells can’t wait to sink their teeth into this tasty treat and greedily suck up the DNA payload inside. It’s the Nutella of the virus world. Seriously, who doesn’t love Nutella? That’s part of what makes COVID-19 so infectious.
The clever scientists at Moderna and Pfizer figured out a way to weaponize this molecular Nutella, and that’s what makes the mRNA vaccine so cool.
The COVID-19 vaccine is just a bit of mRNA (bike messenger) with instructions on how to build the Nutella protein. The vaccine goes into a cell and says “Boss says make this now.” The cell looks at the plans and says “Sure, I can do that.” and goes to work. Soon you have a flood of Nutella protein all over the place, and your cells are in sugar-rush bliss.
That’s it. That’s all the vaccine does- it tells the body to start making the most tasty part of COVID-19. There is no viral payload, not even a part of the virus for your antibodies to attack. The vaccine tells your own body to make a signature protein that will soon become the blueprint for COVID-19 antibodies.
Simple.
Cool!
Not long after this Nutella protein starts making its way through the blood stream, your Immune System looks around and says, “Hey, somethings not right. That thing doesn’t belong here. Kill it!!” Antibodies are made that are specifically targeted at the Nutella protein with one thing in mind- Exterminate!
This process may make you feel pretty sick for a while. You may get a fever, chills, and muscle aches as your Immune System wages war on the streets of your body’s cellular structure. But, when it’s all over, you’ll have no more Nutella protein in your system and you’ll have an army of antibodies primed and ready to kill it if it ever shows up again.
Let’s say a couple of weeks later, you’re infected with COVID-19. Now, instead of being greeted by millions of Nutellla-craving cells, it’ll come face to face with millions of Nutella-destroying antibodies. COVID-19 won’t stand a chance.
Because of the unusual makeup of these vaccines, they must be kept super cold: -94 degrees Fahrenheit for Pfizer and -4 degrees Fahrenheit for Moderna. This makes their distribution and storage a bit of a challenge, but so far American hospitals are up to the task.
That was the best explanation I’ve read!