This article is part of a series explaining the COVID-19 pandemic. Please consider starting at Part 1: What is a virus or check out the whole series by clicking the button below.
What Is A Vaccine?
The first vaccine was used in 1796 when Edward Jenner inoculated an 8-year-old boy with material taken from a cowpox sore on another person, under the hypothesis that having cowpox, which typically has very mild symptoms in humans, would protect against smallpox. Jenner later variolated the boy with smallpox material to test the boy’s reaction: he remained healthy. (HistoryofVaccines.org). As word began to spread about these results it grew in popularity, eventually leading to mass adoption. In fact, the very word, vaccination, is derived from Jenner’s experiment. Vacca is the Latin word for cow. (Science)
Some Terminology
Variolate - As early as 1000CE in Asia, variolation was used as a measure to try and prevent people from dying of smallpox. Variolation is the process of deliberately infecting someone with a controlled dose of smallpox such as dried scabs from smallpox sores.
Innoculate - To implant a microorganism into an environment. In medicine, it typically refers to vaccinations to prevent disease, but in general microbiology, it can be used more generally.
Vaccinate - To innoculate with the specific intent of preventing disease
Immunize - To make someone immune to a disease, to prevent them from getting a disease.
Sources:
National Library of Medicine - Smallpox: A Great And Terrible Scourge
Dictionary.com - “Vaccinate” vs. “Inoculate” vs. “Immunize”: What Are The Differences?
Since then, vaccines have been used as a medical technology to control and, in some cases, eradicate harmful pathogens. As we previously mentioned in our Understanding COVID-19 series, a pathogen is an organism such as “a bacterium, virus, parasite or fungus that can cause disease within the body”
Unlike medicines such as antibiotics, which are usually prescribed once a person has become infected with a pathogen to cure or ease the symptoms of a disease, vaccines work with our natural immune system and responses to prevent becoming infected in the first place, or to reduce the severity of an illness for which you have been inoculated (Immunize BC – What are vaccines?).
“Vaccines train your immune system to create antibodies, just as it does when it’s exposed to a disease. However, because vaccines contain only killed or weakened forms of germs like viruses or bacteria, they do not cause the disease or put you at risk of its complications.”
-World Health Organization
Most, but not all, vaccines introduce weakened or deactivated versions of a pathogen, called antigens, to your immune system through injection, or oral consumption (World Health Organization – Vaccines and Immunization). Once the antigens are introduced, our immune system begins to develop antibodies for that specific antigen, which then combat the pathogen spreading throughout and infecting the body. Our immune system also remembers the antibodies it produces for specific antigens to protect against the same harmful pathogens in the future. This process of developing antibodies and remembering them is called immunization or becoming immune to that pathogen (IMMUNIZE BC – How Do Vaccines Work).
World Health Organization - How Do Vaccines Work?
Side Effects
Because vaccines use damaged or inactivated versions of the pathogen, they are very safe, although there can be side effects. Many people feel some muscle discomfort where they received the vaccine if injected, or a few side effects, this is called an inflammatory reaction. These reactions mean your immune system is hard at work doing its job developing the antibodies to fight the pathogen you were vaccinated for. Common side effects may include muscle aches, fever, chills, or headaches (Government of Canada – Vaccine safety, concerns, and possible side effects).
“It is much safer to get the vaccine than to get the disease it prevents.”
-IMMUNIZE BC
Effectiveness of Vaccines
In the late 18th century, smallpox was a pervasive disease. “On average, 3 out of 10 people infected died of from the disease” (Center for Disease Control - History of Small Pox), while those who survived were left with severe scarring of the skin.
Over time, Jenner’s work inspired others to improve upon the original smallpox vaccine and develop vaccines for additional pathogens such as rabies, diphtheria, measles, polio, and many other diseases, including COVID-19.
On May 8, 1980, 196 years after Jenner inoculated the 8-year-old boy, the WHO declared smallpox eradicated from the planet. (CDC: History of Smallpox)
“We now have vaccines to prevent more than 20 life-threatening diseases, helping people of all ages live longer, healthier lives. Immunization currently prevents 2-3 million deaths every year from diseases like diphtheria, tetanus, pertussis, influenza, and measles.”
-World Health Organization
Infographic: Government of Canada - Vaccines Work
Immunization And Herd Immunity
Vaccinations protect us as individuals against harmful pathogens, but they also help protect others in our communities. Once you become immune to a pathogen by being vaccinated, your chances of spreading the virus are reduced or eliminated.
When enough people become vaccinated against a pathogen in a community, others who cannot be vaccinated are protected, creating an effect called herd immunity, or population immunity. On a basic level, when enough people in a community are vaccinated, pathogens have a difficult time finding a suitable host to replicate in, because the majority of people the pathogen encounters are immune.
When a vaccine becomes available, it is important for as many people to become vaccinated as possible. This is because there are some vulnerable people in our communities that cannot be vaccinated due to underlying health conditions, allergies to vaccine components, or because they do not have access to a vaccine. For example, as of this writing (April 9, 2021), there are no COVID-19 vaccines approved for use in children under the age of 16, though clinical trials are underway.
Watch this brief graphic animation from Harvard Medical School to see how herd immunity works.
Dr. Kara Loos, a genomics research associate from the Institute for Microbial Systems and Society (MISS) at the University of Regina, says that different pathogens require different percentages of herd immunity. For example, Measles is one of the most contagious pathogens on Earth. According to the World Health Organization, it is estimated that 95% of a community needs to be vaccinated against measles to create the required herd immunity to protect the remaining 5% of the population who cannot be vaccinated. By comparison, herd immunity for the polio disease is achieved when about 80% of the population is vaccinated (World Health Organization – Herd Immunity, Lockdowns and COVID-19).
At the beginning of the COVID-19 pandemic, some countries felt that the best way to deal with the disease was through natural herd immunity (Reuters). In all cases, this proved to be disastrous as hundreds of thousands of people died, often overwhelming available health resources. Herd immunity for COVID-19 must be achieved through vaccination. “The proportion of the population that must be vaccinated against COVID-19 to begin inducing herd immunity is not known. This is an important area of research and will likely vary according to the community, the vaccine, the populations prioritized for vaccination, and other factors” (World Health Organization).
An upcoming article will focus specifically on COVID-19 vaccines, and on the different types of vaccines available in the fight against COVID-19. However, this much is clear: the best vaccine for you is the one available to you right now.
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