Living4 types of vaccines that already exist (and you...

4 types of vaccines that already exist (and you should know)


During the development of vaccines against SARS-CoV-2, the already famous coronavirus that causes COVID-19, much has been said about the different types of vaccines that have been tested and licensed. Specifically, vaccines designed with messenger RNA (mRNA) have used a design that has been in the works for the last few decades but has not yet reached clinical trials.

However, the scientific community has had other vaccine designs for several centuries , which have been optimized to achieve a long-lasting and specific immune response for each pathogen.

Various designs for a single function

Vaccines have been one of the most life-saving discoveries in the history of medicine. They have been able to completely eradicate diseases and curb many others.

One of its main advantages lies in its design flexibility, so that it can be adapted to different pathogens.

The mechanism of action of a vaccine consists of presenting the pathogen or a part of it in a controlled situation, to activate the immune system and “teach” it to create defenses against the threat presented in the vaccine. In order for this immune response to occur specifically and to be sufficiently effective and long-lasting, different types of vaccines have been developed and have evolved over time .

Despite some differences in the content of vaccines, they are all designed to be assimilated by the body and presented to the immune system . An important compound in vaccines is the adjuvant. Its name comes from the Latin word adiuvare which means “to help” and which perfectly defines its function.

There are different types of adjuvants used in different treatments (from vaccines to cancer) which have also been improved over time, but they all serve to activate the immune system. Without the presence of adjuvants, it is possible that the organism eliminates the threat (pathogen introduced in the form of a vaccine) without involving the production of cells and defense compounds with memory to act in the long term.

In vaccines, adjuvants accelerate, prolong or intensify the immune response against the pathogen . The biggest differences between vaccines are based on the way the pathogen is presented.

How are the types of vaccines different?

Today we can classify the available vaccines into four main categories :

  • Attenuated pathogen vaccines
  • inactivated pathogens
  • Pathogen subunits (fragments)
  • Genetic material of the pathogen (DNA, mRNA)

Attenuated vaccines

The attenuated and inactivated vaccines were the first to be developed, and the main difference between them is that the attenuated pathogen is still alive, although its virulence and infectivity have been reduced, while the inactivated pathogen is not capable of infecting because it does not its alive. Inactivated vaccines are made up of whole but dead viruses or bacteria.

This type of vaccine, especially the attenuated pathogen, activates the immune system intensely and usually causes side effects of medium severity. The most common are fever, joint pain, swollen glands or lymph nodes, among others.

An example of an attenuated vaccine is known as triple viral, which contains attenuated viruses that cause measles, mumps and rubella .

Inactivated pathogen vaccines

Inactivated vaccines , although they contain the inert pathogen, can also cause side effects. Among the inactivated vaccines we find the vaccine against the Hepatitis A virus or against the bacteria of typhoid fever .

The advantage of this type of vaccine is that the immune response is much more complete and heterogeneous, because the body creates antibodies against many parts of the pathogen.

Vaccines with fragments of pathogens

With the development of biotechnology and molecular techniques, some inactivated vaccines have been replaced by vaccines that only contain parts of the virus or bacteria. This process requires the purification and isolation of fragments of the pathogen, but over time this has been improved with synthesis techniques in cell cultures carried out in the laboratory .

This improvement has made the process of producing pathogen subunit vaccines easier, faster and cheaper. Two examples of this type are the vaccine against the Hepatitis B virus and the Novavax vaccine against SARS-CoV-2, which contains the S (spike) protein of the coronavirus .

Vaccines with genetic information

Finally, there are the vaccines that contain only part of the genetic information of the pathogen and that have taken longer to develop due to the technical limitations of biotechnology and advances in genetic engineering.

Once techniques for isolating genes from viruses and bacteria and introducing them into a vector (another human-safe virus or fat vesicles) were established, they were highly effective at preventing infection.

In this category we can find the Comirnaty vaccine (Pfizer-BioNTech) as an example of a fat nanoparticle that contains protein S mRNA . Vaccines that contain the genetic information of the pathogen in the form of DNA are still in development for humans, but some candidates already exist.

Although today the use of vaccines is widespread throughout the world as a way to prevent many diseases, there are still many techniques that can be improved and new strategies to optimize them.

Undoubtedly, the recent pandemic has refocused attention on this very useful tool and has facilitated the investment and development of mRNA vaccines, which can not only be used for viral infections, but are now being tested for cancer .


Plotkin SA. 2009. Vaccines: the Fourth Century. Clin Vaccine Immunol. doi: 10.1128/CVI.00290-09

World Health Organization (WHO). Immunization coverage. July 2021.

Pardi et al. 2018. mRNA vaccines – a new era in vaccinology. Nat Rev Drug Discov. doi: 10.1038/nrd.2017.243

Regulatory Affairs Professionals Society (RAPS). COVID-19 vaccine tracker. March 2022.




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