Vaccines in the 21st century

Vaccination against infectious diseases has literally transformed the planet. It has succeeded in the elimination of smallpox and the near elimination of polio as scourges of humankind. This kind of success, as well as the great increase in understanding of immunology and the development of new technologies, has increased the hope that new vaccines will target other diseases. Indeed, expectations have been raised so much that vaccines are now being developed not just to prevent infectious diseases but to cure them. In addition, some conditions have now been shown to be related to infectious diseases—for example, human papillomavirus infection has been implicated in cervical cancer and Helicobacter pylori in gastritis, peptic ulcer disease, and stomach cancer—and vaccines should help to prevent or treat these diseases. Other clinical diseases or conditions are also now considered within the purview of vaccines. These include cancers (even those without a known infectious aetiological component), allergies, autoimmune diseases such as diabetes, metabolic diseases such as hyperlipidaemias that lead to atherosclerosis and coronary artery disease, and even addictions such as cocaine and nicotine dependencies.

An examination of the recent advances in immunology and vaccinology provides insights into future vaccine developments. Great strides have been made in understanding how the body distinguishes self from non-self—that is, how the immune system recognises a pathogen as being foreign and hence a target for killing. This is likewise important for understanding why the immune response sometimes becomes too active, resulting in allergies or autoimmune disease. By understanding which cells become activated and knowing what the triggers are, we can try intentionally to stimulate, alter, or suppress the responses.