How do vaccines work?

• Vaccines mimic a natural infection to teach your immune system how to defend itself¹


• Vaccines contain either a weakened or killed form of the microbes that cause infection; they are usually injected into your muscle or under your skin¹


• Certain white blood cells called "macrophages" don't know the difference between these weakened or killed microbes and the real thing, so they eat them and bring them to the lymph nodes


• Once they reach the lymph nodes, the macrophages show helper T cells, a type of white cell called a "lymphocyte," what the antigen parts of the microbe look like, so those cells can recognize them


• Another kind of lymphocyte, called a B cell, can identify antigens on microbes circulating in the system without the help of a macrophage¹


• The T and B cells quickly hunt down and kill the weakened microbes faster than they can reproduce²


• After vaccination, some of the T and B cells are turned into memory cells, which remember what the microbe looked like and keep you protected for years. You now have a supply of infection fighters at the ready, should the real microbes ever attack again²