Scientific American presents House Call Doctor by Quick & Dirty Tips. Scientific American and Quick & Dirty Tips are both Macmillan companies.

Today’s topic will be vaccines and how they work. With all of the controversy surrounding vaccines, I thought that if I am going to make a case for them, I would do little good by giving the standard finger-wagging lecture. People need first to understand infection and immunity before they will accept my claim that immunizations are invaluable. 

What is Immunity?
As I said in my antibiotic podcast, the immune system is the police force of your body. The white blood cells are the officers on the beat, wandering around your bloodstream looking for germs that want to live in your body and cause trouble. If they find a trouble-maker, they promptly identify it and destroy it.

The two main trouble-causing “bad guys” are bacteria and viruses. Both have their tricks to get past your defenses, and both can cause mild or severe infections. But of the two, viruses are the trickier ones, so I’ll focus on them. The theory is the same for either kind of infection.

What Are Viruses?
A virus is a little protein box containing DNA or other genetic material that takes over cells in your body. They are like bad guys who sneak into a country and take over factories so they can send off propaganda to recruit more bad guys to join their cause. The viruses get inside the cells, which are little factories, and make more viruses that can take over other cells to make even more viruses, and so on. The end result is a whole lot of viruses floating around.


Continue reading on