Re: STD Vaccine? (Yuck)

If our body's immune system is so effective at fighting off disease - why then do people die of pathogen-caused illnesses? Have you not heard of the millions who died in 1919 of the 'flu pandemic?!

Don't forget that pathogens have evolved to take advantage of niches within, or a comprimised immune system. If Hep B infected blood splashes on your skin, the Hep B is unlikely to penetrate. However - what happens if you have a small, unnoticed cut in your skin? The virus can bypass the skin, lymph and get straight into the blood. What about malaria? The mosquito injects the parasite directly into your bloodstream - again, the blood would be the first line of defence. Thousands die of malaria every day. A vaccine for malaria would be a wonderful thing. E.coli O157 secrets shiga toxin, so it can eat it's way through the intestinal lining. By doing this it has already gone through the acid of the stomach, and is now going through the M-cells, lymph, and into the blood.

Okay, our pathogen is now in the blood. It has to avoid opsinisation by opsonins. Some bugs can't and are cleared by a combination of the complement system and macrophage engulfment. Some can stearically hinder opsonin attachment, and so progress. Right, antibody - mediated immunity. This varies. Some people can kick out antibodies like George Bush starts wars. These people will be able to keep up with quick - growing organisms (eg menigitis infections). Many, many more cannot do this. Antibody production takes time; certain immune cells have to undergo changes and start producing antibodies. Can the body clear the infection before damage sets in or even death?
By exposeing the person to a small amount of the pathogen in a non-pathogenic state or even dead (pieces of, or whole organisms) organisms, the body will have pre-prepared antibodies ready to go in case the pathogen breaches all the other defences. This is what vaccines are for. They save lives. Look at the rates of menigitis C here in the UK before and after the introduction of the vaccine. It doesn't get much clearer.

Respectfully yours,

Hibes