Immunization and Vaccines: Types and How They Work

Author: Disabled World (DW)
Updated/Revised Date: 4 Aug 2026

Table of Contents:
Synopsis - Definition - About This Section - FAQs - Publications - Subtopics

Synopsis

An overview of immunization and vaccines, explaining active and passive immunization, the diseases vaccines prevent, and school vaccine laws across the United States.

At a Glance

• 1 - Passive immunization works rapidly but is short lasting because the transferred antibodies naturally break down over time.
• 2 - Twenty U.S. states allow philosophical exemptions for those who object to immunizations on personal or moral grounds.
• 3 - The World Health Organization estimated in 2012 that vaccination prevents roughly 2.5 million deaths each year.
• 4 - Four diseases account for ninety-eight percent of vaccine-preventable deaths: measles, Haemophilus influenzae type b, pertussis, and neonatal tetanus.

Topic Definition

Immunization

Immunization is the process by which a person's immune system is strengthened against a specific disease-causing agent, known as an immunogen, so the body can fight or prevent an infection. It is most commonly achieved through vaccination, which prepares the immune system to recognize and respond to harmful microorganisms before illness takes hold. Immunization falls into two broad forms: active immunization, in which a foreign molecule is introduced so the body produces its own lasting defenses through T cells and B cells with their antibodies, and passive immunization, in which ready-made antibodies are transferred into the body for immediate but shorter-lived protection. Recommended for both children and adults, immunization protects individuals from serious diseases such as measles, polio, and hepatitis B, while also helping shield the wider community from their spread.

Overview

Immunization, or immunization, is the process by which an individual's immune system becomes fortified against an agent (known as the immunogen). Immunization shots, or vaccinations, are essential. They protect against things like measles, mumps, rubella, hepatitis B, polio, diphtheria, tetanus, and pertussis (whooping cough). Immunizations are important for adults as well as for children.

Children need immunizations to protect them from dangerous childhood diseases. These diseases can have serious complications and even kill children. Children under 5 are especially susceptible to disease because their immune systems have not built up the necessary defenses to fight infection. By immunizing on time (by age 2), you can protect your child from disease and also protect others at school or daycare.

Immunization can be done through various techniques, most commonly vaccination. Vaccines against microorganisms that cause diseases can prepare the body's immune system, thus helping to fight or prevent an infection. The fact that mutations can cause cancer cells to produce proteins or other molecules that are unknown to the body forms the theoretical basis for therapeutic cancer vaccines. Other molecules can be used for immunization as well, for example in experimental vaccines against nicotine (NicVAX) or the hormone ghrelin (in experiments to create an obesity vaccine).

Passive and Active Immunization

Vaccination is an active form of immunization.

• Active immunization: Active immunization entails the introduction of a foreign molecule into the body, which causes the body itself to generate immunity against the target. This immunity comes from the T cells and the B cells with their antibodies.
• Passive immunization: Passive immunization is where pre-synthesized elements of the immune system are transferred to a person so that the body does not need to produce these elements itself. Currently, antibodies can be used for passive immunization. This method of immunization begins to work rapidly, but it is short lasting because the antibodies are naturally broken down, and if there are no B cells to produce more antibodies, they will disappear.

U.S. Student and Schools Immunization Laws:

All fifty states have legislation requiring specified vaccines for students. Although exemptions vary from state to state, all school immunization laws grant exemptions to children for medical reasons. Almost all states, except Mississippi and West Virginia, grant religious exemptions for people who have religious beliefs against immunizations. Twenty states allow philosophical exemptions for those who object to immunizations because of a personal, moral or other beliefs.

In the U.S. The Immunization Action Coalition (IAC) works to increase immunization rates and prevent disease by creating and distributing educational materials for health professionals and the public that enhance the delivery of safe and effective immunization services. IAC also facilitates communication about the safety, efficacy, and use of vaccines within the broad immunization community of patients, parents, healthcare organizations, and government health agencies.

Serious reactions to vaccines are extremely rare. The risks of serious disease from not vaccinating are far greater than the risks of serious reaction to a vaccination. Diseases for which vaccines are available include:

• Anthrax
• Cholera
• Diphtheria
• Haemophilus influenzae type b
• Hepatitis A
• Hepatitis B
• Hepatitis E
• Human papillomavirus
• Influenza
• Japanese encephalitis
• Measles
• Meningococcal disease
• Mumps
• Pertussis
• Pneumoccocal disease
• Poliomyelitis
• Rabies
• Rotavirus gastenteritis
• Rubella
• Tetanus
• Tick-born encephalitis
• Tuberculosis
• Typhoid fever
• Varicella and herpes zoster (shingles)
• Yellow fever

Immunization Facts and Statistics

• In 2012, the World Health Organization estimated that vaccination prevents 2.5 million deaths each year.
• Before the introduction of vaccines, the only way people became immune to an infectious disease was by actually getting the disease and surviving it.
• Immunizations are definitely less risky and an easier way to become immune to a particular disease than risking a milder form of the disease itself.
• Four diseases are responsible for 98% of vaccine-preventable deaths: measles, Haemophilus influenzae serotype b, pertussis, and neonatal tetanus.
• A vaccine-preventable disease is an infectious disease for which an effective preventive vaccine exists. If a person acquires a vaccine-preventable disease and dies from it, the death is considered a vaccine-preventable death.

Frequently Asked Questions

What is the difference between immunization and vaccination

Vaccination is the act of receiving a vaccine, while immunization is the broader process of becoming protected against a disease, and vaccination is the most common way that immunization is achieved.

Are there side effects from getting vaccinated

Most side effects are mild and short lived, such as a sore arm or a low grade fever, and serious reactions are extremely rare compared with the dangers of the diseases themselves.

Why do some vaccines require booster doses

Protection from certain vaccines can fade over time, so boosters are given to strengthen and extend immunity and keep the body prepared to fight a specific disease.

Can adults still get vaccinated if they missed childhood shots

Yes, adults who missed or are unsure about earlier immunizations can often catch up through recommended schedules, and a healthcare provider can advise which vaccines are appropriate.

How do vaccines help protect a whole community

When enough people in a community are immunized, the spread of a disease slows, which helps shield those who cannot be vaccinated, such as infants or people with certain medical conditions.

Do vaccines contain live viruses

Some vaccines use weakened live organisms while many others use inactivated forms, pieces of an organism, or other materials, and the type used depends on the disease being targeted.

Where can people find the recommended vaccine schedule

Recommended schedules for children and adults are available from healthcare providers and public health agencies, which outline which vaccines are advised and at what ages.

Curated and edited by Ian C. Langtree, Founder & Editor-in-Chief, Disabled World. This section is maintained by the Disabled World editorial team.

Last updated: 4 Aug 2026