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With flu season on the horizon, reviewing the vaccine pathway and how we got to where is worthwhile. We have an amazing and complex immune system. It has several specialized cells, but detection is the first line of an immune response. Detecting a harmful organism that has invaded the body can be surprisingly tricky. This is because cells have to chemically discover specific proteins or sugars on the outside of pathogens. These proteins or sugars can (and do) mutate in quickly-replicating pathogens. Luckily, our immune system can learn the danger of closely-related pathogens. 

Vaccines have a long and storied history. From the first records of vaccines in China hundreds of years ago to the first inoculation against smallpox (using cowpox) to today’s cutting-edge mRNA vaccines, the technology is constantly improving. Here are some of the major ways vaccines are made:

Use a weak virus

The cowpox-smallpox vaccine was an example of a live, whole-pathogen vaccine. This is a type of vaccine where doctors inject small amounts of live viruses into the body. The body responds and becomes inoculated against large doses of the virus in the wild. In the 1950’s live-attenuated vaccines became available. In these, the virus is weakened in a lab so it does not cause serious disease in people. This type of vaccine provides a strong and long-lasting response. Examples of live attenuated vaccines include measles, mumps, and rubella vaccine (MMR), smallpox, chickenpox, and yellow fever. 

Use a dead pathogen

There are other methods to mitigate the problems of live viruses. An inactivated vaccine uses dead virus or bacteria. This makes the vaccine much safer and comes with fewer side effects, but is less effective. The current yearly flu vaccines are inactivated vaccines. Some manufacturers use hen’s eggs to grow the vaccine before inactivation. The resulting vaccine can contain very small amounts of egg protein as a result. The CDC still recommends those with egg allergies get the flu vaccine.

Use part of a virus or bacteria

Subunit vaccines are pieces of a pathogen – generally protein or sugar pieces. These aren’t whole viruses and have fewer side effects as a result. Additionally, these subunits may be able to grant protection against many forms of a pathogen. The Hepatitis B vaccine is an example of a protein subunit vaccine.

Target a dangerous product

Toxoid vaccines such as DPT can help lessen the damage of infection because some bacteria do their damage by releasing dangerous toxins instead of attacking cells. Toxoid vaccines train the body to recognize these toxins as dangerous. Diphtheria and tetanus vaccines are examples of toxoid vaccines. 

Get the body to do the work

Nucleic acid vaccines are a new and different approach that has many benefits. Instead of using a weakened or inactivated pathogen to trigger our immune system, nucleic acid vaccines employ the body to make the vaccines in house. DNA, mRNA, and vector virus vaccines use genetic code created in a laboratory; there is no virus needed to develop the vaccine. Messenger RNA (mRNA) vaccines are the best known and use mRNA, a blueprint for creating specific proteins. When injected into the body, they provide the instructions for our body to produce antigens (proteins) that trigger an immune response. The T-cell and antibody response that follows can fight the disease. This can provide long-lasting, stable, relatively low symptom responses. The real benefit, however, is the time it takes to develop a new vaccine is drastically reduced. This was evident with COVID-19, when researchers created a brand-new vaccine in less than a year. Equally important was distributing it to hundreds of millions of people one year after. A typical vaccine takes 10-15 years to develop – and even longer to scale production.

New studies are coming to compare the effectiveness of mRNA-based vaccines to inactivated vaccines for viruses and diseases beyond covid. Keep a lookout to join this new and developing vaccine research. 

Written by Benton Lowey-Ball, BS Behavioral Neuroscience

References:

NIH, National Institute of Allergy and Infectious Diseases. (2021). Flu vaccine and people with egg allergies. https://www.cdc.gov/flu/prevent/egg-allergies.htm

NIH, National Institute of Allergy and Infectious Diseases. (2019). Vaccine types. https://www.niaid.nih.gov/research/vaccine-types

Greenwood, B. (2014). The contribution of vaccination to global health: past, present and future. Philosophical Transactions of the Royal Society B: Biological Sciences, 369(1645), 20130433.

Boylston, A. (2012). The origins of inoculation. Journal of the Royal Society of Medicine, 105(7), 309-313.