Updated: Mar 31, 2020
Vaccines are very important in preventing many dangerous diseases. Diseases that once ravaged populations, such as polio and tuberculosis, have virtually vanished due to the proliferation of vaccinations. Vaccines are weakened viruses or parts of viruses that do not cause sickness but can still train the immune system to fight pathogens. There are many different types of vaccines that all function in different ways to train the body to fight a pathogen. The vaccines are split into live vaccines and inactive vaccines. Live vaccines contain living weaker pathogens that invade cells and duplicate as if they were harmful viruses. Inactive vaccines do not reproduce in the body, but they still signal an immune response. Contrary to what many believe, vaccines do not actually cause a viral infection to develop. Some sickness symptoms may occur, but they will fade soon after.
The first vaccine was developed by Edward Jenner in 1796. Jenner had realized that people who recovered from smallpox tended to never get it again. Jenner thought that if a patient was exposed to a very similar but less harmful virus called cowpox, they would be immune from smallpox. While the experiment would be inhumane by today’s standards, he injected a young boy with cowpox. After the boy had recovered from the cowpox infection, Jenner injected the boy with smallpox. He found that the boy had developed an immunity to cowpox. He called this injection a “vaccination,” coming from the Latin word “vaccus”, which means “cow.” Now, smallpox has been completely eradicated, with its last recorded case being from the 1970s.
Vaccines work by simulating a real infection. The immune system recognizes a threat and cannot discern that the vaccine is not harmful. T-cells are nonspecific, meaning that they are sent out to attack any invader. B-cells, which are a type of white blood cell, create antibodies to fight the pathogens. These antibodies attack the pathogens and kill them. After the pathogen has been removed, these antibodies and T-cells are stored in case the pathogen attacks again. The second time a pathogen attacks, the immune response is much faster and greater since the body has already seen the pathogen before.
Live vaccines are vaccines that still spread in the body. Two types of live vaccines are similar-pathogen vaccines and attenuated vaccines. A similar pathogen vaccine is what Jenner developed with smallpox, where a very similar but less harmful virus can prevent a much more harmful vaccine. An attenuated vaccine is where a pathogen is altered to where it does not infect the body but it still causes an immune response. Weak pathogens are created in a lab and injected into the body. This type of vaccine is used for many diseases, including measles, mumps, rubella, and yellow fever.
Inactive vaccines do not grow in the body. Types include killed, subunit, toxoid, and genetic vaccines. In a killed vaccine, the pathogen’s shape and other characteristics are kept while the ability to replicate is disabled. The body will still produce a response as if the pathogen was alive and be prepared for future attacks. This type of vaccine is used for polio, typhus, influenza, rabies, and typhoid. In a subunit vaccine, only a small part of the pathogen is used to create a vaccine. For example, only the antigen or protein coat may be used in a vaccine. This way, the immune system will attack the pathogens since it has already seen the antigens present on the virus. This type of vaccine is used for hepatitis B and anthrax. For toxoid vaccines, the vaccine is not training the body to recognize a pathogen, but rather the toxins that the pathogen releases. However, these types of vaccines do not produce a complete immune response and booster shots are needed to maintain immunity. A few examples of diseases that toxoid vaccines prevent are tetanus and diphtheria.
Genetic vaccines, also known as naked-DNA vaccines, are currently in development to try to fight diseases such as AIDS. The idea is that genes from the pathogen could be used to generate an immune response. The genes would insert themselves into body cells, which would produce weaker versions of proteins of the pathogen. The immune response would then build against these proteins, causing immunity. Genetic vaccines are being tested on diseases such as malaria, herpes, influenza, hepatitis B, and HIV.
It is very important that vaccines are widespread. It is much harder for an outbreak to occur if most of the population is vaccinated. This idea of herd immunity means that even if someone is not vaccinated, they are unlikely to develop a disease if most of the population in that area are vaccinated. However, as fewer people are vaccinated, herd immunity decreases. These simple precautionary measures can save many lives and eradicate diseases that were once thought to be invincible. It is much worse to have to deal with a harmful disease than to prevent it early in life.
CDC. (2018, May 16). Vaccines: Vac-Gen/Why Are Childhood Vaccines So Important? Retrieved March 25, 2020, from https://www.cdc.gov/vaccines/vac-gen/howvpd.htm
Department of Health Australia. (2010, July 20). Vaccine-Preventable Diseases. Retrieved March 25, 2020, from https://www1.health.gov.au/internet/main/publishing.nsf/Content/health-pubhlth-strateg-communic-vpd.htm
Discovery Communications (n.d.). Greatest Discoveries: The Beginning of Vaccination [Video File]. Retrieved March 25, 2020, from https://www.sciencechannel.com/tv-shows/greatest-discoveries/videos/the-beginning-of-vaccination.
Groleau, R. (2002, August). NOVA | Killer Disease on Campus | Making Vaccines. Retrieved March 25, 2020, from https://www.pbs.org/wgbh/nova/meningitis/vaccines.html
Hirsch, L. (Ed.). (2019, October). Immune System (for Parents) - Nemours KidsHealth. Retrieved March 25, 2020, from https://kidshealth.org/en/parents/immune.html
Hoyt, A. (2007, October 26). How Vaccines Work. Retrieved March 25, 2020, from https://health.howstuffworks.com/wellness/preventive-care/vaccine1.htm
PLTW. (n.d.). Disease Prevention through Vaccination. Retrieved March 25, 2020, from https://pltw.read.inkling.com/a/b/43d63de35c894eada4e5e54487f3a0bd/p/fff20f0bd7654bd590acc5947968aba3
The College of Physicians of Philadelphia. (n.d.). How Vaccines Work: History of Vaccines. Retrieved March 25, 2020, from https://www.historyofvaccines.org/content/how-vaccines-work