Vaccines and Protection from Diseases
Severe diseases have caused enormous harm to humans throughout history, leading to people looking for ways to prevent diseases from breaking out. Eventually, this quest to prevent outbreaks lead to the development of the practice of vaccination, a procedure where an attenuated or a dead version of a dangerous virus was introduced into the body to provoke an immune response. The idea was then that the injected virus would be weak enough for the immune system to easily defeat it but significant enough for the body to activate its crucial cell memory, leading to a quicker immune response and much better protection if a fully-strong virus of the same dangerous sort was later to show up.
Diseases almost disappearing
In test after test, after the development of the first vaccines, attempts to bring about immunity by administering viruses in a controlled way were deemed successful, and vaccination, therefore, became widespread in the United States during the 1900s. Subsequently, by end of the 20th Century, debilitating diseases like polio and mumps, for which American children were now vaccinated, had become very rare, and smallpox was officially declared eradicated. For this reason, on logical grounds, it was concluded that vaccines combined with such things as better sanitation had practically rid the U.S. of some of the worst scourges humanity had ever seen.
An important key to the vaccine success, as unanimously recognized by U.S. public health officials, was the fact that almost all American children got vaccinated. In this way, herd immunity was achieved, which meant that even those few who could not or would not take vaccines were largely protected from diseases. The protection that unvaccinated people enjoyed, in a practical sense, stemmed from masses of vaccinated immune people creating human barriers that kept sick people from coming in contact with unvaccinated people, and the same concept of herd immunity continue to be important to keep entire populations disease-free today. However, over the last few decades, an increasing number of American parents have begun to opt out of giving their children government-recommended vaccines, risking herd immunity breaking down. This behavior on the part of parents, paradoxically enough, is motivated by a desire to keep children healthy, a rationale elaborated on in the next chapter.