A vaccine Known as a treatment called an antigen or strategic molecule that designed to stimulate an immune response in humans against a pathogen or foreign molecule (virus or bacteria). As a strategic solution for a better response some time, The antigen molecules are mixed with other molecules to enhance the immune reactions in human body. One of strategies for making a vaccine is to use infectious virus or bacteria that has been weakened or attenuated so it would not cause the disease in vaccine receptor, or proteins, nucleic acids, or other molecules that by themselves are not infectious.
Designing a Vaccines is based on prevention from disease, given to healthy individuals to allow the immune system to recognize and mount a response when it comes into contact with a pathogen, rather than therapeutics, given after a person gets the disease.
As a short definition for vaccine, we can say a vaccine is a strategic molecule or solution that is exposed to human immune system in a safe way so that it can learn how to fight off that harmful pathogen and protect your body from it in the future.
Today, vaccines are important because they can greatly reduce and prevent the spread of disease — they have even eradicated some life-threatening diseases worldwide such as COVID-19