Explain how vaccines prevent the one infections

Vaccines help so many different infections. The way the vaccination works will be different for the type of problem there might be. Such as a Tetanus shot will help from getting the Tetanus disease that you may get from puncture wounds, scratches stuff like that,typically from metal. Im not sure if this really helps or not, but hopefully it does a little.

:)

Vaccines do not prevent the infection, but they help shorten the possibility of getting the infection. When getting a vaccine you are really just injecting a small amount of the infection/disease into your system so that your white blood cells can start working at fighting off the disease, that way IF you end up catching the infection, It is no longer foreign to your cells and that way they can fight off the disease quicker. Hope that helps :)

Answera tightly sealed house with an unvented water heater;

I'd say replacing that habit (of smoking) with a more healthy habit, like going to the gym. c;