How Vaccines Work

June 17, 2021

doctor examining a child in a hospital; blog: how vaccines work

According to the World Health Organization (WHO), over 20 million children are still unvaccinated and under-vaccinated worldwide. That’s why they champion World Immunization Week at the end of April each year. The theme for the campaign is #VaccinesWork For All. And they do. Vaccination is one of the most successful and cost-effective ways to protect someone’s health. But do you know how they work?

Immune System Basics

To understand how vaccines work, you have to know a little bit about the human immune system. When germs like bacteria or viruses get into the body, they begin attacking and multiplying, causing an infection that makes you sick. The immune system works to fight infection using white blood cells. 

There are different types of white blood cells with different functions. Some (macrophages)  are responsible for consuming the pathogen (germ), which leaves behind something called an antigen. The other white blood cells (lymphocytes) attack antigens and create antibodies.

The first time your body is introduced to a germ, it can take a while for the white blood cells to ramp up and do their jobs. But once the infection has been cleared, the body remembers how it fought the germs that caused the infection. This is called building immunity.

How Vaccines Work With the Immune System

Vaccines help the body build immunity by imitating an infection. The “infections” vaccines induce do not cause illness, but they cause the body to develop the white blood cells and antibodies needed to protect against an actual infection. Sometimes mild symptoms do develop after a vaccination, but they are very minor and are a sign that the body is building immunity. It takes a couple of weeks after vaccinations for the white blood cells and antibodies to develop. 

Types of Vaccines

There are several different types of vaccines. The type of vaccine needed to protect against illness depends on what kind of infection it is (viral or bacterial) and how the germ cells behave. The five main vaccine types used today are:

  • Live, attenuated vaccines: Fight viruses and bacteria with a version of the living virus or bacteria that has been weakened so it doesn’t cause sickness.
  • Inactivated vaccines: These vaccines fight viruses and bacteria as well, but they contain inactive forms of the germs. The dead germ cells can still cause the body to develop a defense against the antigens. Inactivated vaccines often require multiple “booster” doses to build and maintain immunity.
  • Toxoid vaccines: Prevent diseases caused by bacteria that produce toxins in the body. The vaccines contain weakened versions of the toxins that don’t cause illness.
  • Subunit vaccines: These vaccines contain only a part of the virus or bacteria (called subunits) instead of the whole germ. 
  • Conjugate vaccines: These vaccines are used to fight a certain type of bacteria. The bacteria have an outer coating of sugar-like coatings called polysaccharides. The coating hides the antigen and makes it difficult for the immune system to recognize. The vaccine works by connecting the polysaccharides to antigens that the body already fights well. It teaches the body to have an immune response to the coating as well as the antigen it hides.

How Vaccines Work with Herd Immunity

If you pay attention to the conversations surrounding how vaccines work, you’ve probably heard the term “herd immunity” used. It is also referred to as “community immunity” because vaccines don’t just protect people on an individual basis. They can also protect entire communities and populations. 

Herd immunity kicks in when a majority of people in a population have been immunized. When most people are immune to something, the chances of it being transmitted and causing an outbreak are very low. That protects everyone, including those who are unable to get vaccinated. This is how many dangerous diseases that once spread rapidly and devastated populations have been eliminated without everyone being vaccinated.

Herd immunity is important because there will always be a certain number of people who can’t safely get vaccinated for medical reasons. For instance, very young babies, the elderly, people with severe allergies, pregnant women, and people with compromised immunes systems cannot always get vaccinated for certain things.

Herd immunity does not work unless the people who can get vaccinated do get vaccinated. If too many people choose not to get vaccinated, then there are more places for a virus or bacterium to land and cause infections. This can lead to an outbreak that threatens those who were unable to be immunized for legitimate medical reasons.

At Holly Springs Pediatrics, we recognize the importance of vaccines to your child’s health as well as the health of our community as a whole. That’s why we strongly recommend that parents follow the recommended vaccination schedule for their children. If you have questions or concerns about how vaccines work, call us at (919) 249-4700 to schedule an appointment.