Bob, a Q regarding Vaccines

Winning Hand

Nothing to do whatsoever with the threat of bio warfare.

Can you explain to me the american view of the TB vaccine? I know it isnt practiced there (went through EMT school over there) but here in med school they make you have it, now should I return to america and the bubble test shows up positive for TB antibodies what does that mean? Do they view me as exposed, or do the accept the vaccine as being harmless to others?
Cheers and expect more questions from me in future

Bob the Unlucky Octopus

That's a good question WH, and worth a decent bit of explaining. It's worthwhile, (especially since you seem to be on the way to being a medic :P) to make the distinction between antibody(AB) and antigen(AG). Antibodies(as you'll learn) are globular proteins produced by the B-lymphocytes of our immune systems. Antigens are foreign proteins produced by an invading pathogen. While on occassion they resemble each other, (AIDS, Hep A-C, Hanta, Ebola) 90% of the time they are very different. The purpose of a vaccine is to inject people with antibodies, not antigen...or(and here's where it gets complicated) to inject them with a simplified strain of "killed" antigen so the body can make antibodies against the most basic form of that antigen, usually produced by a virus. This is often used in combination vaccine therapies- MMR for example, or BCG. The only time we have to worry about antibodies adversely affecting others, are in cases when AB closely resembles AG- and in cases when AB residues can be passed on to another generation, and evolve into the AG form.

So here's an example- let us say they manage to invent a vaccine for Hepatitis C...a young girl is vaccinated, and her AB levels are maintained throughout early life. She becomes pregnant, and while the child is gestating, some of her antibodies are passed across the blood-plasma barrier of the placenta. The antibodies, which aren't ready to be processed by the fledgling thymus & immune system of a young child, develop into antigen form, leading to a child being born with Hepatitis C. This is an improbable example of high antibody figures leading to the host becoming a carrier of antigen- but it's not that far-fetched.

The whole thing falls down when you look at viruses where AB and AG are different- such as TB. Tuberculosis is also an airborne virus, most of the time...and as such, it's evolutionary pathway has seperated antibodies against it, from it's own antigen. It never needed to evolve a mutation mechanism- most airborne diseases don't have one.

[rant]
As far as US policy goes, I'm sure they'll give you a hug rather than a frown when you go back- you'll be one of the few people who is immune to the virus, and can't spread it around. We're so frightened of TB back home that we forcibly treat people who cross our southern border who might be carrying TB as a simple antigen. Now to me, that is the most disgusting violation of a person's civil rights- only one step from experimenting on unwilling human subjects...but "in the interests of America's public health and safety" these vaccinations at the border have been going on for decades now. One can only imagine what is being done to border-crossers in the aftermath of the recent anthrax scare.
[/endrant]

I hope that answers your question WH- and I apologize if I did it in a technical or a roundabout way- you'll have to get used to that in med school I can tell you My goal was to give you an overview of how antibody and antigen were distinct...and how on occasion AB made one a carrier. Hope that helped

Occy

Winning Hand

[mel brooks voice] Antigens, antibodies..... whatever , was in a rush at time of composing.
Cheers for the info, now all im concerned about is the 20 inch scar it leaves on your arm (joke)
Your hep C example seems to me to resemble the syndrome of a Rh- mother giving birth to a Rh+ child for the second time, although again, im in a rush so the order might be wrong.

Thanks again m8