Vaccines Shorties: Introduction

It seems that humanity has been divided into two main categories: pro- and anti-vaxxers and the basis of the argumentation lies in oppositional reaction, dramatical oversimplification, and fragmentation of the topic. Let's attempt to start from the basics in a short manner for the purpose of developing a deeper discussion in further posts. The topic itself is multilayered.

The Origins

Possibly, the first notion about knowledge of immunization principles where the Buddhist monks who were known to drink snake venom to confer immunity to snakebite.

The term "vaccine" was used by British physician Edward Jenner and originates from Latin vaccinus "from cows," from vacca "cow,". The earlier term used for the smallpox vaccination was variolation ("variola" - smallpox) and later Louis Pasteur, a French biologist, microbiologist, and chemist started to use the term vaccine for vaccinations against other diseases than smallpox.

It is fascinating to learn that along with the classical "Edward Jenner was the first to introduce the vaccine, the smallpox vaccine to the world", the theory of vaccination and methods of vaccinations were known to the world as early as 200 BC in China or India. It was the practice of inoculation, introducing pathogen (antigen) into a living organism to stimulate the production of antibodies in order to develop a defense against infection.

After surviving smallpox as a child, Emperor K'ang Hsi had his children inoculated in the late 1600s through grinding up smallpox scabs and blowing the matter into nostrils. Another practice was known - scratching matter from smallpox sore into the skin.

The date unknown, this Chinese print shows a vaccination needle From American Medical Association, The History of Inoculation and Vaccination for the Prevention and Treatment of Disease, 1913

Types and differences of vaccines

1. Live attenuated vaccines - vaccines that contain whole bacteria or viruses which have been “weakened” to the optimal state where the vaccine would produce a long-lasting protective immune response, but wouldn't cause the disease. Examples would be MMR (measles-mumps-rubella), rotavirus vaccine, the chickenpox vaccine. Since these vaccines contain a small amount of weakened virus, greater focus and discussion should be provided for people with specific immune dysregulations or other underlying conditions.

2. Inactivated vaccines - Inactivated vaccines are made through using either killed whole bacteria or viruses or small parts of bacteria or viruses such as proteins. Inactivated vaccines usually less long-lasting immune response compared to live vaccines and thus need repeated doses or booster doses.

a) Inactivated vaccines containing whole killed virus: polio vaccine, rabies vaccine

b) Inactivated vaccines containing subunits of viruses or bacteria, for example, polysaccharides (sugars) or proteins from the surface of bacteria or viruses. These vaccines can be divided into toxoid (diphtheria, tetanus, whooping cough), conjugate (pneumococcal vaccine), and recombinant vaccines (hepatitis B vaccine, human papillomavirus vaccine).

Because inactivated vaccines do not cause an adequate immune response on their own (killed viruses or subunits of them do not cause long-lasting immune memory and/or are not immunogenic), they are strongly dependent on adjuvants such as aluminum salts and others (virosomes, squalene, vitamin E and others). There are around over 30 different adjuvants licensed for use in different vaccines. The adjuvants are known to either act as a certain vehicle for the vaccine (injected antigen) or act as immunostimulants.

For example, Aluminum salts are known to trigger an innate immune response through dendritic cells which then activates "stronger" immune response to the vaccine antigens through the recruitment of antigen-presenting cells. However, there has been an understanding that despite the rapid progress in the antigen and adjuvant design, knowledge gaps remain in our understanding of the immune system. A deeper understanding of the mode of action of adjuvants will also facilitate the evaluation of the safety profile of new adjuvanted vaccines (DiPasquale et al 2015).

3. Third-generation DNA vaccines consist only of DNA (as plasmids) or RNA (as mRNA), which is taken up by cells and translated into protein. These vaccines have their pro's and con's like all others but in many ways, they pave the wave for a greater level of a more specific immune response. The positives: they are highly immunogenic, easy to manipulate, genetically stable. The negative side so far has been the low efficacy due to production specifics.

Although there are a few subcategories of the vaccines, the structure is provided here to start diving deeper into the topic. When we tell "vaccines", we also need t to understand that we often need to focus on a more specific subcategory because their way of action and the way of production differs greatly