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How Do Vaccines Work?

March 8, 2022

When we think of vaccines, most of us think of the common childhood shots we all had to get when we were younger: chicken pox, measles, mumps– the illnesses you were vaccinated for once and seemingly never had to worry about contracting from then onwards. Think to yourself for just a moment: have you ever had chicken pox, or come down with a case of measles or mumps? Can you think of a friend or family member that’s contracted one of these diseases? Perhaps you know one or two, but they’re certainly not common sicknesses, such as the flu or the common cold. It’s more likely than not that you’ve never experienced any of these illnesses.

Why is it that there are so few cases of these diseases now? Less than one hundred years ago, measles, mumps, chicken pox (otherwise known as varicella), and many more killed hundreds of thousands of people every year, and medicine did little to protect people from their dangerous side effects. However, once a vaccination was created, the amount of people contracting these deadly illnesses decreased significantly. 


Vaccines are unlike standard medically-prescribed drugs in many different ways. First of all, vaccines are designed as a method of prevention rather than treatment. Unlike typical medication, almost always prescribed after an illness has already been contracted, vaccinations provide protection against a disease before the recipient is even infected. The reason you’ve never had chicken pox isn’t because you’ve taken your vitamins– it’s because you got vaccinated! Most of us don’t even remember getting vaccinated against these scary illnesses, and that’s because it often happens when we’re very, very young. The measles, mumps, and rubella vaccine, also known as the MMR vaccine, is given to infants when they’re about one year old. The Center for Disease Prevention and Control (CDC) states that “Children should get two doses of MMR vaccine, starting with the first dose at 12-15 months of age, and the second dose at 4 through 6 years of age.” During this timeframe, many children also receive their vaccination against chickenpox, and their legal guardians can opt to provide them with either Varivax, containing just the chickenpox vaccine, or the ProQuad vaccine, a shot that vaccinates against measles, mumps, rubella, and chickenpox, all in one injection.

Many vaccinations, including the type that prevent against dangerous illnesses like the measles and mumps, focus on exposing the body’s immune system to the “bacteria, virus, or other pathogen” causing the disease (Gavi: The Vaccine Alliance). Once a body’s immune system has had time to process a very small amount of the bacteria causing these illnesses, it can learn how to combat these bacteria head-on when potentially faced with them in the future. The human body has a tremendous “memory” of the initial exposure to the bacteria through the shot, and it can often “last many years, or in some cases for life”, another reason behind the lasting effectiveness of vaccines (Gavi: The Vaccine Alliance). There are two common types of these vaccines: live-attenuated vaccines and inactivated vaccines. 

Live-attenuated vaccines contain a weakened strain of the bacteria that causes the disease the shot is aiming to prevent. This type of vaccination is one of the strongest, and can teach the body how to protect itself against illness for an entire lifetime. Often, live-attenuated vaccines are only needed one throughout your entire life! However, for certain people, these vaccines can pose certain dangers if their immune system is not equipped to fight off the weaker bacteria, and they risk getting infected by the disease. However, for most people, these vaccines are perfectly safe, though it is recommended that you always speak to your healthcare provider prior to receiving one. The MMR vaccine and chickenpox are both examples of live-attenuated vaccines.

Inactivated vaccines “use the killed version of the germ that causes a disease” (U.S. Department of Health and Human Services). While often believed to be safer because the germ inside is dead, the immunity they provide is often not as powerful as live vaccines. As a result, many inactivated vaccines require multiple doses of one injection, so as to ensure the human body remains protected even as time goes on. The most commonly known examples of inactivated vaccines include the flu shot and Hepatitis A shot.

Antibodies are proteins that the human body makes in order to defend itself against illness. Once a vaccine is given to someone, the small strain of harmless bacteria injected into the body is then analyzed by the immune system, and it learns how to defend itself against future versions of their bacteria that can be harmful if ignored. 

However, not all vaccines work like this. Instead of injecting a body with an existing strain of the illness-causing bacteria or other pathogen, some vaccinations opt for alternative methods. Some vaccines use genetic material - information taken from our DNA or RNA. DNA, the abbreviated term for deoxyribonucleic acid, and RNA, the abbreviated term of ribonucleic acid, can teach our cells how to create an antigen against disease. This antigen will protect our body in the future in case we ever get infected. These vaccines are known by a number of different names, such as a nucleic acid vaccine, and a messenger RNA vaccine, known as mRNA. They have significantly shorter processing times than many other types of vaccines, and there is no risk of accidentally infecting the person getting the vaccine, since there is no live virus inside (U.S. Department of Health and Human Services). The COVID-19 vaccine uses RNA technology, and serves as an example of an mRNA vaccine. 

There is another type of vaccine that uses information from DNA to produce antigens. It’s known as the viral vector vaccine. This vaccine uses “a harmless virus as the ‘vector’ or carrier - which is different from the one the vaccine is targeting” (Gavi: The Vaccine Alliance). Once injected, instructions derived from the DNA are transported into the body, and the cells learn how to combat potential infection. The rVSV-ZEBOV Ebola vaccine acts as a primary example of the viral vector vaccine.

Certain vaccines use an antigen to “trigger an immune response to a germ” (Gavi: The Vaccine Alliance). Sometimes called protein subunit, polysaccharide, and conjugate vaccines, these shots combine two antigens, typically one weaker with one stronger, and teach the body how to produce a powerful immune response in the case of infection. The MenACWY vaccine is a terrific example of a conjugate subunit vaccine.

A toxoid vaccine uses a controlled amount of toxin produced by the germ causing a particular disease. Thix toxin, when injected in a small amount, develops protection against not the entire germ, but rather the parts of the germ that actually cause the disease. Due to this focus on solely the harmful parts of the germ, the immune system spends its time fighting only the dangerous strains, and ignores the safe parts of the germ. A tetanus shot is an example of a toxoid vaccine, and is needed every ten years for optimal protection.

While there are many types of vaccines being created each day, these are the most commonly used throughout the medical field. Despite their unique approaches to protecting the body from disease, they all work to teach the human body how to counteract infectious bacteria in different ways, and keep our immune systems safe from potential danger. 

How Do Vaccines Work?: Research
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