Controversies about vaccination
Perhaps one of the most important advances of medicine during the 20th century was the improvement of vaccination techniques. The accumulated knowledge not only about infectious diseases, mainly viral and bacterial, but also regarding the immune response against such diseases led to a deep comprehension about how "to teach" human immune system to fight such certain pathogens even before being exposed to them.
On the pre-vaccination era, human immune system was able to learn how to fight diseases only after a first contact with the etiologic agent and even when this is a good way to fight flu and some other minor diseases in other cases such as polio, where an uniques exposure would not only teach the immune system to fight the disease (as it certainly will) but also could lead to lifelong, negative sequelae.
After vaccination development science was able to teach the immune system to fight virus and bacteria without first suffer the disease. To do so, certain proteins known as antigens, each one specific for certain disease are inoculated into the human body, doing that the immune system is able to recognize such antigens and once an organism with them enters the body, it will be ready to fight against that infection avoiding this way the disease development as well long term complications..
At this point everything seems to be OK but after massification of vaccination certain safety issues were detected. On this regard, as any other therapeutic method, vaccines have potential negative side effects as well as potentially lethal complications. Such situation led to continued improvement of vaccines in order to optimize their effect while diminishing as most as possible every potential side effect in order to provide as much protection as possible without jeopardizing kids safety.
Unfortunately still the complication rate is not 0, and even when it tends to be less everyday, there's a group of people real concerned about potential vaccination risks and avoid any kind of vaccine.
Of course their worries are justified but after a numeric analysis it seems that vaccination has more pros than cons.
On the last 50 years major viral outbreaks of diseases such as chickenpox, rubella and measles disappeared while polio related complications have not been seen on the last 4 decades. Considering such a infectious diseases dramatic reduction and the fast rise of human population on the last century, the benefit of vaccination may be numbered on hundreds of millions patients.
On the other hand, complications even when possible, are less than 1 in 100.000 vaccinated patients; thus the chance of problems is too small and doesn't outweigh the benefit. On this regard it's more dangerous car traveling than vaccination but unfortunately every day more and more people is deciding to avoid vaccines for their kids.
The impact of such behaviour won't take too long to show, in fact outbreaks of diseases such as measles have been seen more on the last 5 years than on the previous 4 decades and that's only the beginning.
When it's time to decide whether to vaccinate or not your kids, it's mandatory to balance risks over benefits, and currently benefits still outweigh risks, something that should keep that way due to continuos vaccination improvement.
Of course it's possible that particular cases could need special attention, on such situations proper medical advise is strongly recommended