Vaccines are not natural:

Some parents are concerned about vaccinations not being "natural".   They feel it is introducing to their child's body artificial products in an un-natural way.  There are many issues that go into the concept of what is "natural". 

Do vaccinations trigger an un-natural immune response?

First, many of the vaccines introduce the same type of immunity that the child would get if they caught the disease naturally.  This is how vaccines work:  they stimulate the immune system to recognize either some part of the virus or a weakened strain of the virus.  That way, the next time the virus is encountered, the system is already aware and ready to respond, so the child does not get the full-blown disease or does not get sick at all.  In order to gain immunity without vaccination, a child must first be exposed to the virus.  This wild type of the virus causes the classic illness.  Although not much fun, most children come through these illnesses just fine.  There is a small percentage, however, who develop serious complications or even die from these diseases.  This is one of the reasons that the vaccines are used.  Vaccines are designed to replace this first and most dangerous exposure so that the body is better equipped to respond if the virus is encountered later.

Vaccines are given via an un-natural route:

Some argue that although real virus particles are used, it is un-natural to introduce them directly into the body via an injection instead of the natural route of exposure through the mouth, nose, etc.  Indeed, it is seen that a higher percentage of the population gains complete immunity to an organism when they contract the disease through natural means.  However, natural exposure also results in a much higher percentage of people who get ill and develop serious complications.  The effectiveness of the vaccination must be weighed against the risks.  There is always a percentage of the population who do not develop immunity even after getting vaccinated according to the recommended schedule.  There are a few who will never respond to a particular vaccine.  This is known and thus the goal of vaccinating the population is to minimize susceptibility, not eliminate it. 

 Some vaccine can be given orally or via nasal spray.  The influenza vaccine (flu shot) can be given via nasal spray.  The body responds to the weakened form of the virus in the same way as it would to the wild type.  The polio vaccine is one that can be given either orally or intramuscularly (injected).  The oral polio is no longer recommended in the US because this was a live attenuated (weakened) vaccine that had a risk of being shed in the stool of children after they received it.  Because it was a live vaccine, there was a theoretical risk of it mutating into a virulent type that could then infect others.  Because of this theoretical risk, the switch was made to the injected vaccine, even though it is slightly less effective in producing immunity. 

Vaccines contain other additives that are un-natural:

Besides the immunogenic particles, vaccines also contain many other foreign substances.  Other agents are necessary in order to prepare a vaccine.  Some help stabilize the substance, some make the body respond to the virus particles more vigorously, and sometimes preservatives are used to ward off bacterial growth. None of these products have been proven to cause adverse effects in the amount that they are present in vaccines. 

Another issue to consider is all of the other sources of exposure to "un-natural" products.  Very few people live a truly primitive "natural" existence.  The modern world is filled with plastics, food-additives, pesticides, synthetic fibers, and air pollutants.  Many parents who are concerned about vaccinations are concerned about these issues as well, and this is not an either/or proposition.  Trying to minimize exposure to all types of potentially harmful substances does not sound like an unreasonable prospect.  However, parents must consider both sides of the issue when deciding whether or not to vaccinate.  If vaccines had no up side, they would not be recommended and any risk would be too much.  However, since they also offer benefits, this must be weighed against the risks of a small amount of exposure.   

Can healthy living be a substitute for vaccinating?

Some make the argument that if a person is optimally healthy through good diet and healthy living, then that person is not susceptible to diseases.  This is only partially true.  Good diet and healthy lifestyle can make an individual less susceptible to disease and these individuals often recover from disease more quickly.   It is not 100% effective however.  Some people can be in great health but be exposed to a particularly virulent or infectious agent and still get sick.  Otherwise healthy children would frequently get chicken pox before the vaccination was available.  Vaccinations can be something to be done in addition to having a healthy diet, exercising, managing stress, and doing other things to promote health.  It is not an either/or proposition.  In addition, a healthy lifestyle can help individuals cope with the multitude of illnesses and viruses for which there are no vaccines. 

Is all traditional medicine un-natural?

It can be argued that the entire field of medicine goes against what is “natural”.  Illness and death have existed throughout history and throughout nature.  Modern medicine attempts to use human technology to counter these forces.  In the past, many children would die of now treatable or preventable infections.  A parent must consider, if they are willing to forgo vaccinations because it is not natural, are they also willing to forgo all treatment for that disease if their child contracts it? 

Links:

Addressing Parents' Concerns: Do Vaccines Contain Harmful Preservatives, Adjuvants, Additives, or Residuals?

Vaccination Debate (an anti-vaccination page)