A preparation containing usually killed or weakened microorganisms (as bacteria or viruses) that is given usually by injection to increase protection against a particular disease.
How the white blood cells respond to a vaccine?
Each vaccine contains a small amount of the disease (virus or bacteria), or at least a few parts of the germ. Examples of vaccines that contain parts of the germ is: measles virus, whooping cough bacteria, and tetanus toxoid. But, the vaccines do not cause disease because the germs are either dead or weakened and the toxoids are inactive.
How long the vaccine will be effective for?
An injection is inserted into a patient carrying the vaccine with a dead or altered form of the disease-causing pathogen. These dead or altered pathogens carry a specific antigen. This causes the immune system or the white blood cells to produce antibodies.
What happens in the case of a real infection after vaccination?
White blood cells respond to a vaccine by producing antibodies, which target and attach to the antigen.
Vaccines vary for how long they are effective for. Most vaccines are effective for 15-20 years.
When a high percentage of the population have been vaccinated, it is difficult for infectious diseases to spread, because there are not many people who can be infected. Also, this makes it harder for the disease to spread from person to person.