Are vaccinations at all useful if they’re given after exposure to whatever disease-causing microbe they’re intended to fight? Or do the antibodies need time to establish themselves in one’s bloodstream before they’re at all effective? Does the answer depend at all on the type of vaccine? (I seem to recall rabies vaccine normally being given after exposure…)
Related question: is receiving a blood transfusion an effective way of gaining antibodies? Or even possible?
Just as a hypothetical, suppose I’ve been exposed to cowpox and now have antibodies that give me immunity to smallpox. Suppose also you have been exposed to smallpox from whatever source. Assuming I’m Type O, and we transfuse a pint of blood from me to you, what happens?
Rabies and tetanus vaccines are both commonly given after exposure. IIRC this is because the diseases develop slowly enough that the response from the vaccine occurs faster than any symptoms. WIth rapidly developing diseases presumably it wouldn’t work.
Well snake bite anti-venom is just a concentrated dose of horse antibodies, so the idea is quite sound in theory. However I suspect that the concentration of antibodies in whole blood would normally be so low as to be useless. The only excpetion would occur if the victim already had a fatal toxin/microbe load in which case you would only be making your condition worse with the transfusion.
I’m guessing nothing. Remeber the amount of circulating antibodies is persihingly small if the victim isn’t currently suffering from the infection. So someone exposed to smallpox 20 years ago won’t have enough circulating antibodies to fight my infection today.
Some vaccinations are helpful if given after exposure; rabies, hepatis B, and measles vaccines all come to mind. However, in each case, it is advised to give immunoglobulin (antibodies) at the same time. Vaccines always work best if given before exposure. In general, a person is not considered to be protected against a disease until a week or so has elapsed after vaccination (or completion of the series if more than one dose is required).
A transfusion of whole blood could be of some benefit because some people have levels of antibodies that are 10 or 100 times the protective level. So if you got a unit of blood from someone with 100 times the protective level, you would have about 10 times the protective level.