When germs or viruses, such as SARS-CoV-2 virus that causes COVID-19, invade the human body, they start attacking cells and multiply. You may have come across the term antigens, which is the category name of all germs, viruses or other harmful microorganisms invading the human body. The invasion is called an infection.
As part of the human immune system, white blood cells fight infections by removing germs, viruses and infected human cells. During this removal process, the immune system creates antibodies. Each type of antibody is unique and defends the body against one specific type of antigen.
Vaccines help the bodies develop immunity without us having to get the illness, by simulating an infection. The immune reaction to the vaccination leaves “memory” cells that will remember how to build the needed antibodies and how to fight that virus in the future.
The development of these “memory” cells take some weeks after the vaccination.