A vaccine is said to provide immunity from certain infections and diseases. In a sense a vaccine is homeopathic, as it uses a little bit of the disease itself to galvanize the body into producing antibodies against it. Once the body has produced these antibodies, they may be automatically reproduced to fight the disease or infection for many years.
The term vaccine comes from Edward Jenner who discovered in the late 1700s the mechanism that vaccines apparently use. Jenner experimented with cow pox in order to develop an inoculation against small pox.
Despite the many breakthroughs claimed for vaccines, they are increasingly controversial in the 21st century as children and adults are exposed to more and more of them. Giving children a number of vaccines before they are five or six years old is bound to strike some as excessive, especially when some are live-virus vaccines. That Western governments increasingly seek to mandate vaccines only aggravates the controversy.
In fact, there is plenty of anecdotal evidence about the destructive nature of vaccines when they apparently collide with the wrong genetic or biological type. Opponents of this kind of apocryphal dialogue will point out that it means nothing without scientific rigor. And yet there seems much of it, especially on the Internet.
Most children apparently can easily tolerate vaccines (for better or worse) but perhaps some cannot. There seems to be an ever-increasing amount of asthma, immune system related syndromes and other "chronic" conditions (in addition to autism) that modern Western medicine cannot easily explain. Vaccine opponents are convinced that the over-application of vaccines may have something to do with it.
Why is there not more research into the potential damage that vaccines may cause? Critics argue that if vaccines are as safe as their makers proclaim, then they should welcome such research and pursue it themselves. That would silence the naysayers once and for all.