Why Do The Vaccines Cause Sore Arm?
A few days ago I got my first jab of the COVID-19 vaccine. It started to hurt in the arm around where the vaccine was injected. It felt like someone had punched me on the arm. I felt like Joey from Friends in that episode where his girlfriend was a little loose with her fists.
Then I started to wonder: Why does the arm hurt after vaccination? I brought out the scientist in me and started researching. Here is what I found out!
The pain and inflammation is the response of our body to the foreign substance being injected, the mighty mRNA (Messenger Ribonucleic acid) that codes for the spike protein of the virus. This mRNA gives the body a preview of what the virus might look like. The spike protein by itself is not capable of causing the viral infection, but it helps our body prepare the antibodies that target these conserved spike proteins.
When our body is challenged with a pathogen or any other invading substance, it releases a storm of defence responses. One of these responses is inflammation, where the body sends cytokines and other white blood cells to the area of invasion to neutralize the foreign substance. The pain that we experience after the shot is the consequence of this. These immune cells rush to the area of injection and build up layers of tissue. This causes pressure to build up around the nerve endings and pain signals to the brain are sent as a consequence.
Every time the body is exposed to the same infection again, its immune response is stronger than the last because our body remembers every virus that tries to invade it. This is why the second dose hurts more than the first one. The body recognizes the spike protein from the first shot and doubles down in terms of the immune response for the second shot. The graph below shows the concentration of antibodies that are secreted after first and second exposure to the infection.
In a sense, the pain that we experience after the vaccine injection is a good sign, because it means that the immune system is working to generate the antibodies for the adjuvant.
