The non-antibiotic part of the immune system really is incredible. The stomach to blood barrier is so effective that in a healthy and uninjured person, ingesting infected bodily fluids even the HIV virus which is infamous for tricking the immune system will be destroyed long before it has a chance to enter the bloodstream.
The flu virus actually bypasses that as its primary point of infection is through the eyes and directly into the bloodstream. A lot of other viruses travel through the same pathway and no amount or diet and lifestyle choices can protect us from having airborne viruses in our bloodstream (short of wearing goggles any time we leave the house).
The blood based immune system also has some incredible tricks up its sleeve. The blood itself (well, the white bits in the blood) will attack anything that shouldn’t be there and there are things the body does such as expelling contaminated mucus and elevating body temperature to become inhospitable to heat sensitive microorganisms. Sometimes the immune system is a bit too focussed on killing the infection and will accidentally kill the patient too which is still good for the species as a whole because the virus can’t spread as far… at least that was the case before air travel and densely packed cities.
The thing is, the human immune system works faster when it has encountered something before. A virus that we’ve had and survived we will never have again, and if we do encounter a mutated form of the virus, our body is only a few short steps from creating the antidote. Being exposed to a range of dead virus cells from the particularly nasty varieties at a young age gives the body a chance to learn a few basic tricks for fighting them, and if it does encounter something similar but mutated, the symptoms are reduced and so is the recovery time.
As long as we keep immunising kids, the really nasty viruses can’t gain enough of a foothold to mutate into something our body can’t manage. Some of them will continue to spread because of high mutation rates, but the symptoms will be reduced. It is a clever way of teaching kids’ bodies how to fight off particular types of infection for the rest of their lives. It bypasses the skin and stomach wall guards because that’s what viruses that actually cause infection do.
There is the concern of heavy metals in an immunisation. A single vaccination shot contains around 25 micrograms of a mercury based anti-pathogen (Thimerosal) to protect the vaccine from contamination by harmful bacteria. To put this into perspective, this is more mercury than a single tuna sandwich but less than the build up of mercury from a tuna sandwich in the lunchbox once a week for a year. You’d be exposed to greater quantities of heavy metals by drinking two litres of tap water per day over the same duration. The benefit of this additive is that it prevents dangerous pathogens from entering the bloodstream with the dead virus cells and reduces the likelihood of the injection causing an infection.
We have an amazing immune system. Vaccines don’t bypass the system. They strengthen it.