Sore arm after vaccination?

During vaccination, a part of the virus is introduced to our cells (in the case of COVID-19, the spike proteins). Our immune system recognize these vaccinated cells as infected/foreign and our first line of defence - the innate immune response, is activated. This is a protective mechanism of our body against any exposure to foreign materials, from a splinter to bacteria to virus, and their goal is to eliminate these intruders! This leads to inflammation where immune system cells release substances to make blood vessels wider for more immune cells to arrive, causing the site to swell, which is why we might experience a sore arm after vaccination. All these occur within the first few days of vaccination, and this occurrence is not limited to any vaccines – e.g. Hep B, chicken pox vaccines, etc. ⁣⁣⁣

Here are some readings if you’re interested in learning more!

The Conversation “No, vaccine side effects don’t tell you how well your immune system will protect you from COVID-19” 19 Apr 2021

National Geographic “Why your arm might be sore after getting a vaccine” 19 Mar 2021

Khan Academy “Innate immunity”

“The safety of Covid-19 mRNA vaccines: a review” Patient Saf Surg 15, 20 (2021).

Molecular Biology of the Cell. 4th edition. New York: Garland Science; 2002. “Innate Immunity.” Available from: https://www.ncbi.nlm.nih.gov/books/NBK26846/

“Current Challenges of iPSC-Based Disease Modeling and Therapeutic Implications” Cells 2019, 8, 403 (30 Apr 2019)

“Induction of Pluripotent Stem Cells from Mouse Embryonic and Adult Fibroblast Cultures by Defined Factors” Cell 126, 663–676 (25 Aug 2006)