Vaccines and vaccination: history and emerging issues

Abstract

Prophylactic vaccines are crucial in modern healthcare and have been used successfully to combat bacterial and viral infectious diseases. Infections like polio and smallpox, which were dreaded historically, and which devastated the human race over many centuries, are now rare. Smallpox has been eradicated completely and polio is nearly eradicated because of vaccines. Vaccines differ fundamentally from other classes of medicines in that they are usually administered as a preventive measure to a healthy individual rather than to a sick person already with an infection, although exceptions to this practice exist. Most currently used prophylactic vaccines are based on established platforms, but many vaccine candidates, in late development stages, including several COVID-19 vaccines, use highly novel vaccine platforms not available historically. History of infectious diseases and prophylactic vaccines are filled with important scientific lessons, and thus provide valuable insights for the future. With hindsight, historically there were some ethically questionable approaches to testing vaccines and the germ warfare against native populations in the Americas and other regions. In this review, we examine key historical lessons learned with prophylactic vaccines with reflections on current healthcare dilemmas and controversies with respect to influenza and COVID-19 vaccines.

Keywords: Vaccines; history of vaccines; infectious diseases; preventive medicines; prophylactic vaccines; vaccination; virology.

Figure 1.

Different types/classes of vaccines. Vaccines are produced using different processes. Vaccines may contain live attenuated pathogens (usually viruses), inactivated whole pathogens, toxoids (an inactivated form of the toxin produced by bacteria that causes the disease), or parts of pathogens (e.g., natural or recombinant proteins, polysaccharides, conjugated polysaccharide or virus-like particles). Adapted from.

Figure 2.

A highly simplified representation of the SARS-CoV-2 cell cycle. (A1) Virus entry generally occurs via surface glycoprotein (Spike protein, S-protein) binding to ACE2 receptor, TMPRSS2 also has a critical role to play in this process. Detailed interactions between S protein–ACE2 are also shown (courtesy of Dr. Serdar Kuyucak, USyd (A2). The virus can also enter by endocytosis (B&C). Subsequently, uncoating of viral proteins, primary translation, polyprotein processing and transcription take place. (D). Translation and viral RNA synthesis then occur (E). Other key steps such as accessory protein-host interactions take place prior to assembly and viral maturation. (F). Finally, release of mature viruses occurs via endocytosis.