Why Immunize?

There are many reasons to immunize. But first, let’s look at the immune system, what vaccines are and how they work.

How does the immune system protect me against diseases?

This slideshow will walk you through the process.

Invading pathogens, such as viruses and bacteria, enter the body. Their surfaces contain antigens, which are proteins or sometimes fats or sugars.

The immune system senses the presence of antigens. It knows that the invader doesn’t belong. Three types of immune cells — macrophages, dendritic cells, and B cells — attack and devour some of the pathogens and absorb their antigens.

Immune cells that have absorbed antigens become antigen presenters. They display the antigens on their surfaces so that other immune cells can see what the intruder antigens look like.

Antigen presenters travel to the lymph nodes, where lots of immune cells gather, waiting for instructions. The antigen presenters show the antigens to the waiting cells.

Seeing the antigens activates additional B and T cells, including T-helper cells. Activation readies them to fight the specific pathogen displaying those antigens.

Activated T-helper cells help coordinate the rest of the immune system responses. The immune system attacks the invader in several ways:

Activated B cells become factories that produce and release hundreds of millions of tiny proteins called antibodies. The antibodies are designed to fit precisely onto the antigens of the invading pathogen. They swarm bacterial cells or free-floating viruses, latch onto the antigens, and prevent the pathogen’s ability to do harm.

While the immune cells are working together to defeat the infection, B cells, T cells, and T-helper cells also create memory cells. Their job is to remember the pathogen and how to fight it. If the invader returns, the memory cells begin fighting it before the person even gets sick.

Activated T cells can become T-helper cells or T-killer cells. T-helper cells trigger other immune cells to kill bacteria and body cells infected by viruses.

During viral infections, viruses enter the body’s cells and hijack them, instructing the cells to create more viruses. The T-killer cells look for antigens on hijacked body cells and destroy them.

Illustration from Vaccination Investigation written by Tara Haelle. Text copyright 2018 by Tara Haelle. Reprinted with the permission of Twenty-First Century Books, a division of Lerner Publishing Group, Inc. All rights reserved. No part of this excerpt may be used or reproduced in any manner whatsoever without the prior written permission of Lemer Publishing Group, Inc.

What is a vaccine?

A vaccine is a “biological preparation” that stimulates the body’s production of antibodies to provide immunity against disease. According to the World Health Organization (WHO), vaccines usually contain “an agent that resembles a disease-causing microorganism, and is often made from weakened or killed forms of the microbe, its toxins or one of its surface proteins.” This agent triggers the body’s immune system to recognize it as foreign and destroy it. The immune system will remember the agent so that it can destroy the intruder if encountered with it again.

NOVA | Immunity and Vaccines Explained | PBS

How do vaccines protect my family’s health?

When you vaccinate your children, you protect them from a variety of diseases that used to cause suffering and death for thousands of Americans a year, and many more deaths around the world. Outbreaks of measles, rubella, whooping cough, polio and other contagious diseases once meant numerous missed school days, quarantines, and hospitalizations. All of these are preventable with vaccines for these illnesses.

How do vaccines protect public health?

Vaccination helps build herd immunity. Herd immunity means that a high enough percentage of people in a community are immune to a disease, and the disease cannot easily spread to vulnerable hosts. When herd immunity, also known as community immunity is strong, even people without immunity, like newborns, or people with compromised immune systems, are protected.

Every year, immunizations prevent an estimated 2-3 million deaths from diphtheria, tetanus, pertussis, and measles among people in every age group. Children are disproportionately affected by these life-threatening diseases. (UNICEF, 2013)
In 2011, 123 countries immunized more than 90% of infants against measles. Between 2000 and 2011, vaccination resulted in a 71% decrease in measles deaths worldwide. (UNICEF, 2013)
Thanks to immunizations, smallpox was eradicated, with polio following closely behind. (WHO, 2012)

Are vaccines safe?

The current U.S. vaccine supply is the safest in history (CDC, 2015). While like any medical intervention, there are always potential side effects, most associated with vaccines are minor, especially when compared with the risk of contracting a potentially life-threatening disease. Side effects vary from vaccine to vaccine, but the most commonly reported ones are swelling and/or soreness at the injection site, and low-grade fever.

What vaccines do I need and when? How about my kids?

Where can I get myself/my family vaccinated?

In San Francisco, there are numerous free and low-cost options. The San Francisco Department of Public Health runs the Adult Immunization and Travel Clinic (AITC), a non-profit, fee-for-service clinic. AITC is a full-service travel medicine provider for individuals, groups and families, and offers TB testing and routine immunization for adults and teens.

You can find a list of other options here: https://www.sfcdcp.org/immunizations/where-to-get-immunized/