Exploring the different types of vaccines

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Vaccines are a hot topic, and for good reason. They have saved millions of lives and saved many from debilitating diseases such as Polio. There are a few different COVID-19 vaccines that have been developed in the past year. In this blog, we explore the different types of vaccines.

There has been much misinformation about vaccines. Most notably, Andrew Wakefield falsely claiming that the measles, mumps, and rubella (MMR) vaccine causes autism. This is, however, patently untrue. After his allegations, many people refused to give the vaccines to their children. As a result there were multiple outbreaks of measles throughout the world.

The COVID‑19 vaccine is intended to provide acquired immunity* against severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2). This is the virus causing coronavirus disease 2019 (COVID‑19). Before the COVID‑19 pandemic, work to develop a vaccine against coronavirus diseases like severe acute respiratory syndrome (SARS) and the Middle East respiratory syndrome (MERS) established knowledge about the structure and function of coronaviruses. This knowledge enabled accelerated development of the different types of vaccines technologies during early 2020.

*Acquired immunity is the process that creates immunological memory after an initial response to a specific pathogen (in this case, a virus). This leads to an improved response to future encounters with that pathogen. Antibodies are a critical part of the adaptive immune system. Adaptive immunity can provide long-lasting protection, sometimes for the person’s entire lifetime. For example, someone who recovers from measles is now protected against measles for their lifetime; in other cases, it does not provide lifetime protection, as with chickenpox. This process is the basis of vaccination.

As of February 2021, eleven different types of vaccines are authorized by at least one national regulatory authority for public use:

RNA vaccines (Pfizer–BioNTech vaccine and the Moderna vaccine)

An RNA vaccine or mRNA (messenger RNA) vaccine uses a copy of a natural chemical called messenger RNA (mRNA) to produce an immune response. The vaccine inserts molecules of synthetic RNA into immunity cells. Once inside the immune cells, the vaccine’s RNA functions as mRNA, causing the cells to build the foreign protein that would typically be produced by a pathogen (such as a virus) or by a cancer cell. These protein molecules stimulate an adaptive immune response which teaches the body how to identify and destroy the corresponding pathogen or cancer cells. A co-formulation of the molecule achieves the mRNA delivery into lipid nanoparticles that protect the RNA strands and helps their absorption into the cells.

The use of RNA in a vaccine has been the basis of considerable misinformation circulated via social media, wrongly claiming that the use of RNA alters a person’s DNA or emphasizing the technology’s previously unknown safety record while ignoring the more recent accumulation of evidence from trials involving tens of thousands of people.

Inactivated vaccine (killed vaccine) (BBIBP-CorV, Covaxin, CoronaVac and CoviVac)

This is a vaccine consisting of virus particles, bacteria, or other pathogens that have been grown in culture and then killed to destroy disease-producing capacity. In contrast, live vaccines use pathogens that are still alive (but are almost always weakened). Pathogens for inactivated vaccines are grown under controlled conditions and are killed as a means to reduce infectivity and thus prevent infection from the vaccine. The virus is killed using a method such as heat or formaldehyde.

Viral vector vaccines (Sputnik V, the Oxford–AstraZeneca vaccine, Convidicea, and the Johnson & Johnson vaccine)

A live vector vaccine is a vaccine that uses an organism (typically a virus or bacterium) that does not cause disease to transport the pathogen genes into the body to stimulate an immune response.

Peptide vaccine (EpiVacCorona)

A peptide vaccine is any peptide that serves to immunize an organism against a pathogen. Peptide vaccines are often synthetic vaccines and mimic naturally occurring proteins from pathogens. In addition to infectious pathogens, peptide vaccines can be utilized as therapeutic cancer vaccines, where peptides from tumour-associated antigens are used to induce an effective anti-tumour T-cell response. Synthetic long peptides (SLP) have shown promising successful results.