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Immunity: How Covid-19 Vaccines Work

by Deborah Landry, Ph.D.

Pages 2 and 3 of 18

How Covid-19 Vaccines Work
By Deborah B. Landry, Ph.D.
How Covid-19 Vaccines Work
By Deborah Landry, Ph.D.
© Deborah Landry, 2021-23.
All rights reserved.
Have you ever wondered how your body defends itself against germs or how vaccines work? This book explores the immune system, the role of specific immune cells, and how the new Covid-19 vaccines enhance your immunity and protect you from disease.
Your Immune System
The immune system is a living shield that defends you against bacterial and viral infections and other diseases. It is made up of many organs and specialized immune cells.
The tonsils, located in the back of your throat, and the lymph nodes, located in your neck, armpits, groin, and elsewhere, have specialized immune cells that prevent infections.

The lining of your intestines, mainly for digesting food, contains an enormous number of immune cells that protect you from germs. Skin is a flexible living barrier that prevents fluid loss, protects you from harmful things in your environment, and has immune cells roaming throughout it, hunting for invaders.

The thymus, located above your heart, and the spleen, located in your abdominal cavity, both play an important role in producing immune cells.
Organs and Cells of the Immune System


Intestine Lining



White Blood Cells

Bone Marrow
White blood cells, found in your blood and in organs, play a key role in fighting infections. Bone marrow, found inside your bones, contains stem cells that produce new white blood cells (and red blood cells) when they are needed.
Your Innate Immune System is Always Present
Your innate immunity is always present and ready to fight foreign invaders. It includes natural barriers—like your skin and the mucous membranes of the nose, mouth, lungs and eyes—that prevent germs from entering your body.

Innate immune cells have a variety of protective functions including: sparking a fever to fight off an infection, killing infected cells and tumor cells, and alerting the adaptive immune system (discussed later). Scavenger cells, like macrophage cells, continuously hunt for and engulf "foreign" germs (and debris) and then, activate the adaptive immune system.
Natural Barriers Like Skin
Macrophage Cell
Scavenger Cells
The Adaptive Immune System Learns to Fight Germs
Your adaptive immune system includes specialized white blood cells, called B cells and T cells. They are activated by innate immune cells and must "learn" to attack specific germs. Therefore, your adaptive immunity is slower to respond.

When B cells become active, they produce antibodies, which stick to germs or infected cells. This complex is removed from the body with the help of complement (part of the innate immune system).

When T cells are activated, they kill infected cells and prevent the spread of infection, or they bolster the immune system by making stimulatory molecules.
B cell
B-cells make antibodies to kill germs
T-cells kill infected cells
T cell
Your Immune System Has Memory
After you recover from an infection, a portion of the activated B and T cells (that fought the virus or bacteria) remain in your lymph organs in a dormant state. They are called memory B cells and memory T cells.

If you are exposed to the same infectious agent again, at a later time, your memory B and T cells respond more quickly and aggressively than the naive "inexperienced" B and T cells did during your first exposure. The memory cells rapidly multiply, migrate to the infection, attack the infectious agent and clear it from your body before you get sick.
B cell
Memory B cell
T cell
Memory T cell