First, I’m just an engineer, I am NOT a medical doctor.
So, to answer your question as best as I am able. Your body develops anti-bodies to infections that it has encountered. Once you encounter an infection, your body will is triggered to mass produce the appropriate anti-body.
Your body does not know a vaccine from the real deal; both result in your immune system producing antibodies. The antibodies do not know, or care whether they were created from a vaccine or an infection.
After you have overcome an infection, there is no reason for your body to keep the population of antibodies around, as too many antibodies in your system just creates problems. So, the population drops; but it does not drop to zero. They are stored, or the means to reproduce them is stored (magically, as far as I can tell).
So, if a disease with a long gestation period comes up; your body has a chance to rebuild those antibodoes to fight off the infection before you are aware of any symptoms. We call this immunity.
However, if you ever get a 24 hour bug that comes on fast, and you bounce back quicker than your coworkers who are down for days - chances are that the bug was a fast mover, and your body took 24 hours to rebuild the defence from this known bug.
Immunity means that your body has seen and defeated this bug. It does not mean that this particular bug will never again make you sick in the future - however you will be less sick than if you had never had the bug at all.
Is it wiser to have the vaccine or the illness? The vaccine usually takes 2 weeks to give you immunity, so many people get a shot on Monday and get sick on Friday - then blame the vaccine as being useless. The fact is that many bugs have a 3-7 day incubation period. They were sick either before they got the shot; or got sick well before the vaccine had triggered the immune response.
The more shots you have, the more bugs you can statistically avoid (no such thing as 100% immunity to anything). It’s all an odds game, I’d rather have 30% likelihood of not getting the Swine Flu than 100% certainty of getting it if I’m infected. With the Swine Flu being a brand new bug to the human race - no human has immunity (except those who have now either had the shot, or had the illnesss). This bug is rather benign this year. What will the Swine flu mutate into next year?
Oh, and just as an FYI. Our bodies are miraculous things. Our bodies not only react to the specific bug that made us sick, they also react to SOME variations of the bug. Thus, if you got a flu shot 5 years ago, you may have been susceptable to the flu variation that went around in the prceeding years because your body identified it as the origional bug - that doesn’t mean that this year’s mutation will also work. It’s all an odds game.
I appreciate your response and I could tell by some of your other posts that you are an educated person. I am a doctor, but not the medical kind. I am a biochemist and molecular virologist. The recent public outcries about vaccine safety has inspired me to do some research of my own on flu vaccines. There is so much confusion, misinterpretation and junk science on the web that it is no surprise that so many are scared.
What I was referring to in my post to you was the difference between vaccine acquired immunity versus natural immunity from infection. It is well known in the field that while natural immunity is lifelong, this is not necessarily the case with vaccination. For some reason, the immune system tends to “forget” vaccine acquired immunity over time. This is why booster shots are required. It seems that the body does actually know the difference between a vaccine and an infection.