By this, I mean how long after a vaccine is given is an animal protected against the disease? I understand that some vaccines are not necessarily 100% effective, so let’s say how long until the animal is as protected as it’s going to be?
For example, if my cat gets a feline leukemia vaccine right now, and is somehow exposed to the virus one minute later, my guess is that the vaccine has not yet had time to educate the immune system as to how to fight that virus, and kitty is as likely to get feline leukemia as if it had never been vaccinated. How about the following day? Week? Month?
I’ve heard of people getting rabies vaccines after they have already been bitten by a possibly rabid animal. How does that help? Doesn’t the real virus have a head start?
Or is it different for different diseases? Can some vaccines confer immunity faster than others?
Purely a hypothetic question, BTW, and not a request for medical advice. I’m not planning to expose any animal or human to any disease.
I’m not sure about the general part of your question, but I can answer the part about rabies.
Rabies vaccines work even after you’ve been exposed because the rabies virus travels fairly slowly through your nerves, from the area of infection up into the spine and then up into the brain, but you’re okay until it reaches your brain. So the vaccine sensitizes the immune system everywhere else, and by the time the virus would have gotten to your brain (hopefully), your immune system can deal with it, preventing you from actually coming down with the always-fatal[sup]1[/sup] neurological symptoms of rabies.
I say “hopefully” because obviously it will take the virus a lot longer to get into your brain if you get bitten on the finger or the leg than it will if you get bitten on, say, the face. The closer the area of infection is to the brain, the faster the virus can get there, so it becomes critical to get the vaccine as soon as possible.
Only one person has ever survived once rabies symptoms have actually begun without ever getting the vaccine – Jeanna Giese. Unfortunately, her treatment hasn’t worked for anybody else so far…
[sup]1[/sup]Almost always fatal – there are only six known cases of survival after symptoms develop, most of which were cases of vaccine failure, where the vaccine was administered but it failed to fully protect the victim.
Vaccine response varies by type of vaccine, host (vaccine recipient) and disease being vaccinated for. In approximate terms, 1-3 weeks is probably reasonable.
We give Rabies Immune Globulin along with Rabies Vaccine when we see someone who needs to be treated for Rabies exposure (assuming they have not already been vaccinated). For a potentially rabid bite, for example, we infiltrate the area around the bite with the RIG. The idea is for the already-formed antibodies in the RIG to combat the virus while the body is producing a response to the vaccine.
In the case of feline panleukopenia (and other animal viruses), it takes about 2 weeks for the immune system to respond and make antibodies to it, provided the response has not been intercepted by maternal antibodies. And in that case, as with many other vaccines, the response is not that great, so a booster shot is given that creates a bigger response by the immune system (anamnestic response) that is more effective and longer lasting. After the booster shots, the vaccine may only need to be given annually (or even less), just to create another anamnestic response.
Giving the booster vaccine a week after the first shot is not effective as the body has not had time to mount an immune response with IgG and memory cells by that time (all that it has the IgM response, the first antibody produced in response to an antigen).
Along with what has been said already, let me add that some vaccines (including IMHO, feline leukemia vaccine) do a poor job of protection regardless of how they are used. Imagine an HIV vaccine that was 60% effective. You might argue it would be “better than nothing”, however avoiding exposure would still be the ideal way to go.
Also, the time needed for an individual to mount a response is affected by numerous variables. For example, if the animal has had prior exposure to an antigen, the an-amnesiac response can be very rapid.
It is a term used by a virologist I once knew. Basically, the immune system “remembers” past exposure and responds more quickly in subsequent exposure.
I don’t wanna derail the OP with linguistics/semantics, but I see equal google hits for both terms, with “anamnestic” hits leaning more toward a patients history, and “anamnesiac” occurring more in immunology references, especially those in veterinary literature. Maybe all the vet referencers know the same virologist? .
Is there a general difference in acquiring immunity to a virus vs. a bacteria? That is, can you build immunity to a bacteria faster or slower than to a virus? Or is it all still in the land of It Depends?
I am fascinated by that…must be a difference of the Google Home Page we are using. My apologies. I get 276,000 responses for anamnestic anamnestic - Google Search, including this definition from the Veterinary Dictionary: http://www.answers.com/anamnestic&r=67
*anamnestic
pertaining to anamnesis.
aiding the memory.
a. response-a secondary immune response; occurs with a second or subsequent exposure to an antigen. The antibody or cell-mediated response is more rapid and greater than occurred following the primary exposure.*
I get nothing of any value for anamnesiac; 1,690 cites of no particular theme… anamnesiac - Google Search I’ve only heard the term “an amnesiac” used to refer to the guy who can’t sleep.
MLS, Generally speaking much of immunity is to various markers, such as surface proteins. It’s not to the whole thing you are getting immune to–i.e. it’s not to the entire virus or the entire bacterium. So the response depends. It depends on a number of other variables as well.
