Vaccines

A vaccine is a biological preparation, usually given by injection, which improves or conveys immunity to a particular disease. Most vaccines are made from dead or weakened viruses or bacteria, from fragments of these microorganisms or from the toxins they produce. Vaccines are quite different from chemical medicines; they usually have much more complex molecular structures than chemical medicines because they are produced through natural processes. In contrast to most chemical medicines, they are frequently given to healthy individuals and normally aim to prevent rather than cure disease. Therefore, it is important to ensure that any risks of side effects are minimal.

Background

The potential for vaccines to save lives was first discovered in the late 18th century, when Edward Jenner noticed that milkmaids who had previously contracted the cowpox virus seemed to be resistant to the similar, but more deadly, smallpox virus. To test his theory, he infected 8-year-old James Phipps with cowpox and then later attempted to infect him with smallpox. As expected, Phipps did not develop the smallpox virus, proving Jenner’s hypothesis to be correct. A global vaccination plan was implemented in the 20th century, which eradicated smallpox.¹ Vaccines are now available for preventing many previously devastating diseases, such as polio, typhoid, measles and tuberculosis, and have saved millions of lives worldwide. Indeed, today, vaccines are being used not only to prevent diseases, but also to treat diseases as well, such as cancer.