Types of Vaccinations

Table of Contents

How do vaccines work?

The immune system responds to germs by producing antibodies. Antibodies fight the germs off. They can remain after the germ leaves the body. This is why you can only catch some sicknesses once. Antibodies are specific. This means each pathogen has its own antibodies. If two viruses have similar shapes, the same antibodies can provide protection. Vaccines allow the body to fight against infection, without being infected first. After receiving a vaccine you immune system works hard to make antibodies. This can make you feel tired, have headaches, or even develop a fever. These symptoms normally only last a few days, and do not mean you are infected with the virus.

Antibody Structure
Antibody Structure. Purple shaded region can bind and inactivate a pathogen, Credit: flickr.com/Model of the VRC01 Antibody" by NIAID is licensed under CC BY 2.0

Inactivated Vaccines

Inactivated vaccines use dead germs. The dead germs are injected into the body. The body produces antibodies in response. However, it typically does not produce enough to prevent infection. As a result, multiple doses may be required. Each dose increases the amount of antibodies. Over time, the body builds up enough antibodies to prevent infection.

Why use an inactivated vaccine?

Inactive vaccines are often cheap to produce. You have likely received an inactive vaccine. Both the flu and polio vaccines are inactive vaccines. Providing inactive vaccines to rural regions can be difficult because they require multiple doses.

Live-Attenuated Vaccines

Live-attenuated vaccines work in a similar way to inactive vaccines. However, the virus is still alive when it’s injected!

 

The word “attenuated” means “weakened.” It may sound crazy to inject a living virus into a patient, but the germ is weak enough that it will not cause infection. The body will produce antibodies in response to the weak virus.

What was the first vaccine?

The first ever vaccine was a live-attenuated vaccine. It was against smallpox. Patients were inoculated with a virus similar to smallpox: cowpox. Cowpox is not fatal in humans. The patients’ bodies made antibodies against cowpox, and so they could also resist smallpox.

 

Live-attenuated vaccines are still used today. Some common ones include the chickenpox and the MMR vaccines. This type of vaccine produces many antibodies, and so often requires only one or two doses to reach immunity. In rare cases, they can cause sickness. This happens most often in people with weak immune systems. It’s important to see a doctor before receiving one. The vaccines also needs to be kept cool. This can make it difficult to transport them to rural areas.

mRNA Vaccines

The mRNA vaccine is a new type of vaccine. However, mRNA technology has been progressing for decades.

Discovery and Timeline of mRNA vaccines, Credit: Wikimedia/Arthur Esprit, Wout de Mey, Rajendra Bahadur Shahi, Kris Thielemans, Lorenzo Franceschini, and Karine Breckpot is licensed under CC BY 4.0.

What is mRNA?

The “m” in mRNA stands for messenger. RNA stands for ribonucleic acid. RNA has a structure that is complementary to DNA. DNA is copied into RNA, which is then translated into proteins. The typical process for protein production goes DNA-> RNA-> Protein. Similar to DNA, RNA is made up of the same basic code in all living things. This allows viruses to hijack cells and make their own proteins.

What’s the difference between traditional vaccines and mRNA vaccines?

Traditional vaccines inject the patient with a weak or dead form of the virus. mRNA vaccines provide instructions on how to make a viral protein. The viral protein produced will not cause infection. The body will then make antibodies which target the viral protein. Cells also break down mRNA quickly after it is used.

DNA to RNA to Protein
DNA to RNA to Protein Credit: Wikimedia/Madprime is licensed under CC BY-SA 3.0

The Moderna & Pfizer Covid-19 vaccines

The Covid-19 vaccine is an mRNA vaccine. Sars-CoV-2 is the virus which causes Covid-19. It has a large surface protein called the spike protein. The vaccine contains mRNA coding for the spike protein. Your cells make the spike protein, and then the body produces antibodies which target the spike protein. When someone catches Covid-19 later, they’re able to fight the virus.

Toxoid Vaccines

Typical vaccines focus on helping the body kill germs. Toxoid vaccines target a molecule the germ produces. Bacteria often cause infection by producing a toxin. Antibodies can target the toxin rather than the germ. The tetanus vaccine is a toxoid vaccine. Toxoid vaccines usually need booster shots to stay effective over time.

Virus-Like Particles

The body will make antibodies if it *thinks* there’s a virus, even if there is not. Virus-like particle (VLP) vaccines use a molecule whose structure is similar to the virus. However, the VLP does not contain any viral DNA. Essentially, a VLP is “sheep in wolves’ clothing.” As the particle “looks like” the virus, the antibodies are effective against the virus. VLP vaccines include the HPV vaccine.

Viral Vector Vaccines

Viral vector vaccines use viruses’ ability to invade cells to their advantage. A “vector” is something which carries DNA to cells. Viruses inject host cells with their DNA. Host cells then turn the DNA into viral proteins. This means viruses are good at delivering DNA to cells. A viral vector vaccine uses a virus to deliver DNA instructions on how to make antibodies. The viral vector no longer delivers its own DNA. This means it will not cause sickness. Additionally, the viral vector is not the virus the vaccine is for.

Johnson & Johnson Vaccine

The Johnson & Johnson Covid-19 vaccine is a viral vector vaccine. It uses a common cold virus. The vector delivers DNA to make the spike protein. The cells then make antibodies in response to the spike protein.

CoronaVirus Spike Protein
CoronaVirus Spike Protein Credit: flickr.com/National Institutes of Health (NIH) is licensed under CC BY-NC 2.0.

Glossary

Antibodies: Proteins produced by the immune system to fight germs

 

DNA: Codes genetic information for all traits in a living organism

 

Inoculate: To introduce a substance into the body to stimulate the immune system and prevent infection

 

mRNA: Type of RNA that is an intermediary between DNA and proteins

 

Pathogen: A germ or small particle that can cause infection in plants and animals. Includes viruses, bacteria, and fungi.

 

Proteins: Type of nutrient found in plants and animals. Used for many cell functions.

 

RNA: Similar in structure to DNA. Reads, or transcribes, instructions from DNA. There are many different kinds of RNA that carry out various functions in cells.

 

Sars-CoV-2: Virus which causes Covid-19 infection

 

Spike Protein: Surface protein of Sars-CoV-2 and other viruses

 

Vaccine: Mixture which stimulates the body’s immune system to produce antibodies and prevent infection.

Reading Score: 60.28

 

Grade Level Score: 7.14

Dai, L., Gao, G.F. 2021. Viral targets for vaccines against COVID-19. Nat Rev Immunol 21, 73–82. https://doi.org/10.1038/s41577-020-00480-0

 

Office of Infectious Disease and HIV/AIDS Policy (OIDP). “Vaccine Types.” HHS.gov, 6 Dec. 2021, https://www.hhs.gov/immunization/basics/types/index.html.

 

Moynihan, C. “What Are Virus-like Particles and Why Are They Important?” Pollock Research Lab, 15 July 2019, https://blog.richmond.edu/pollocklab/2019/07/05/what-are-virus-like-particles-and-why-are-they-important/.

 

Plotkin S. 2014. History of vaccination. Proc Natl Acad Sci 111(34):12283–7. doi: 10.1073/pnas.1400472111. Epub 2014 Aug 18. PMID: 25136134; PMCID: PMC4151719.

 

“What Is the difference between an mRNA and a viral vector vaccine?” CT.gov, 06 July 2021, https://portal.ct.gov/vaccine-portal/Vaccine-Knowledge-Base/Articles/mRNA-vs-Viral-Vector?language=en_US.

Copyright @smorescience. All rights reserved. Do not copy, cite, publish, or distribute this content without permission.


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Author

  • Erin Kelley

    Erin graduated magna cum laude from Rensselaer Polytechnic Institute(RPI) with a Bachelor's degree in Bioinformatics and Molecular Biology, and earned a Master’s of Science in Biochemistry & Biophysics from RPI. She loves writing for Smore Science because it allows her to share her passion for science with a large audience! Erin competed for RPI’s Varsity Cross Country & Track team and was even the team captain. At RPI she researched genetically modified E.Coli for vaccine development. Erin explored many career interests in college, and she currently works as a biologist, but also loves chemistry, computer science, & environmental science.