Many ask what it is that happens after you inject a vaccine. How exactly do vaccines work?
What is immunity and for how long does it last?
If babies get antibodies that protect against infectious diseases from a mothers breast milk then why do we need to vaccinate?
Let us try to answer these questions in the simplest manner possible. To do this we will need to divide the immune system into 3. We will call these the innate immune system, the adaptive immune system and the memory part of the immune system. The vaccine is injected either under the skin (subcutaneous e.g. Measles, Yellow fever), into the skin (intra-dermal e.g BCG vaccine) or into a muscle (intra-muscular e.g Hepatitis B, PCV, DT, Td, TT, DTwP, DTaP, Hib). Some vaccines like the Polio Vaccine and Rotavirus are given orally.