Why Is It Always the Upper Arm
There's good reason why vaccines are injected into the upper arm muscle and for kids, the upper thigh muscle. These areas of muscle tissue optimize vaccine immunogenicity, which is how well the site prompts the body's immune response and the magnitude of that response over time. Even the length and gauge of the needle matter and can be chosen to reduce pain at the injection site which muscle also reduces making serious side effects rare.
Among the current crop of COVID-19 vaccines are two that use mRNA to instruct your own cells to make a piece of the SARS-CoV-two virus called the spike protein. Your cells make the protein which the body recognizes as foreign and activates the immune system to protect you. Both are proven to be safe and effective and are injected into the upper arm.
As a child, I got my vaccines in the backside but we know now that's not a good spot. Fat cells are not good for starting an immune response compared to muscles. Muscles have antigen presenting cells that take in foreign substances, show them to other immune cells to fire up our immunity. Fat also slows the vaccine's flow into the blood stream, again slowing our immune response. Poor drainage in fat can cause discomfort and enzymes can destroy parts of the vaccine if it stays there too long.
Well, I gladly traded a few days of sore upper arm for the protection the COVID-nineteen vaccine gave me.
More Information
The importance of injecting vaccines into muscle
Most vaccines should be given via the intramuscular route into the deltoid or the anterolateral aspect of the thigh. This optimises the immunogenicity of the vaccine and minimises adverse reactions at the injection site. Recent studies have highlighted the importance of administering vaccines correctly...
Why do we get shots in the arm? It's all about the muscle
Millions have rolled up their sleeves for the COVID-19 vaccine, but why haven't they rolled up their pants legs instead? Why do we get most shots in our arms? As an associate professor of nursing with a background in public health, and as a mother of two curious kids, I field this question fairly often. So here's the science behind why we get most vaccines in our arm...