My big question is: Are vaccines safe?
This post, I will be looking at: How do vaccines work?
In order to understand how vaccines work, we must first gain a basic understanding of our immune system. I’ve done a lot of research about this in order to be able to summarize it briefly in this post. Our immune systems are very complicated, but in short, we have two main immune responses:
- Innate response – This is a non-specific response to pathogens, which makes it quick to react. It can be split into two parts, external/chemical defences, and internal defences.
- Adaptive response – This is a specific response to pathogens, which makes it slower than the innate response. It does however, have a memory, which is how we build immunity.
Vaccines work with our adaptive immune system to help us build immunity to viruses we have not yet been introduced to. There are a number of different cells in the adaptive immune system, but these are the basic ones:
Macrophages – These are a kind of white blood cell. Their job is to swallow up and digest germs and dying cells. The macrophages leave behind pieces of the eaten intruders (antigens) so that antibodies can learn to identify them.
B-cells – These are also a kind of white blood cell. These cells are defensive cells, and they produce antibodies, which help fight against the intruder.
T-cells – T cells are unique, because they don’t attack the intruder, but they attack your own cells that are already infected to prevent a spread. They do this by inducing apoptosis, which is essentially cell self destruction
Vaccines imitate infection in order to prepare your adaptive immune system. During this simulation, the body’s cells will learn how to combat said infection. If your adaptive immune system is already familiar with a particular virus, it can react quicker if need, eliminating the problem before you even notice. (1) (2)
But how exactly does a vaccine simulate infection? Well, it depends on the kind of vaccine. Here’s a list of different kinds of vaccines, and how they function:
1.Live, attenuated vaccines – These vaccines are for fighting viruses and bacteria. They contain a weakened, live version of the virus/bacteria. These kinds of vaccines normally need to be kept cool, so they can be hard to transport, especially in countries with limited refrigerator access.
2. Inactivated vaccines – These are also for fighting against viruses and bacteria. They contain an inactivated or dead version of the virus/bacteria. Inactivated vaccines aren’t usually as strong as live ones, so a booster shot is often needed to maintain immunity.
3. Messenger RNA vaccines – This is a fairly new kind of vaccine, using mRNA to produce proteins that trigger an immune response. The risk of this kind of vaccine causing disease is considered to be lower, since no real live virus is being injected. This is the kind of vaccine used to protect against COVID 19.
4. Subunit, recombinant, polysaccharide, and conjugate vaccines – These vaccines contain only specific parts of the germ/virus it builds immunity against. This causes your immune system to focus on familiarising itself with one key part of the germ. The downside to this kind of vaccine is that you often need to get booster shots to keep immunity.
5. Toxoid vaccines – These vaccines contain the toxin produced by the germ rather than the germ itself. This means it builds immunity against the toxin produced, not the germ.
6. Viral vector vaccines – These kinds of vaccines are really new, and they DNA that produces the antigen for a specific germ. (3)
The image above illustrates how inactivated vaccines work. Since the vaccine cannot replicate, the B-cell has as much time as it needs to find out which antibodies can defend against the virus.
Some videos I watched before working on my post to gain a general understanding of the immune system and vaccination:
All photos are from Sketchy Science: Infecting with Immunity: How Vaccines Actually Work ! I recommend checking out, it’s a very fun explanation.