Exploring the Development of Vaccine Platforms, With a Particular Focus on the COVID-19 Pandemic

Vaccines have been a cornerstone of human health for more than 200 years and one of the most important tools to reduce childhood deaths caused by pathogens. The concept of vaccines is basically to take something safe, make it immunogenic and induce an immune response in the host that will protect it against something dangerous. Live attenuated vaccines were the only option two centuries ago. These are excellent, and possibly the best vaccine platform, but they have limitations as they cannot always be given to everyone safely, for example due to deficient immunity or pregnancy. That is why newer platforms, such as killed or inactivated vaccines, were developed. These provide better all-round safety, but are often less immunogenic and require additional doses. Subcomponent vaccines were then developed in the 1980s. These only used parts of the virus, further improving safety and introducing the possibility of producing vaccines using gene technology. Adding genetic vaccines to the toolbox revolutionized the way that we handled the COVID-19 pandemic. The host became the producer of the vaccine, which better mimicked the immune responses induced by the live attenuated vaccines. All these platforms will be discussed in this mini-review.