If you want to start with facts, start with this...
vac·cine
/vakˈsēn/
noun
a substance used to stimulate the production of antibodies and provide an immune protective response against one or several diseases, prepared from the causative agent of a disease, its products, or a synthetic substitute, treated to act as an antigen without inducing the disease.
In other words, the vaccine stimulates and primes the natural immune system to be able to respond to an infective agent and be well prepared to defeat it. It doesn’t stop it from getting on board, but helps your body be ready and able to repel the invader.
Repelling the invader and destroying it is what the immune system is designed to do. A vaccine is like a training drill for the immune system to deal with an invader and it’s tactics that the immune system has never seen before so it can be ready to defeat it.
Think of the Military, if they didn’t train for new threats and tactics they wouldn’t be ready to fight them effectively and defend us from being destroyed. Your body is no different. The vaccine is the “war game” your body needs to be ready for the real war when the virus invades.
It really is just that simple...and nothing more than that.