December 2020

Vaccines are a marvel of the modern age. They have help to eradicate a number of diseases that affected large parts of the population. In 1796, Edward Jenner used cowpox material to create immunity to smallpox. His innovations led to the eradication of smallpox. In the middle of the 20th

century, research and development was extremely active. Growing viruses in laboratories led to rapid discoveries and innovations including the creation of the polio vaccine. Researchers began focusing on childhood diseases like measles, mumps, and rubella. These vaccines led to a rapid decline in disease.

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Many of the terms associated with vaccines are used interchangeably, so let’s start with defining and distinguishing these words.

Immunity: Protection from an infectious disease. If you are immune to a disease, you can be exposed to it without becoming infected.

Vaccine: A product that stimulates a person’s immune system to produce immunity to a specific disease, protecting the person from that disease. Vaccines are usually administered through needle injections, but can also be administered by mouth or sprayed into the nose.

Vaccination: The act of introducing a vaccine into the body to produce immunity to a specific disease.

Immunization: A process by which a person becomes protected against a disease through vaccination. This term is often used interchangeably with vaccination

or inoculation.

How do vaccines work?

Vaccines contain the same germs that cause disease. However, the germs have been killed or weakened to the point that they won’t make you sick. Some vaccines only contain part of a germ.

When someone is vaccinated, they are injected with the weakened or inactive germs. The body detects the germ and begins to mount an immune response. After mounting an attack, your body will remember this germ invader so that it can attack it if the immune system ever encounters it again. Some vaccines provide life-long immunity while others require boosters to keep providing immunity.

What are the side effects of vaccines?

Any vaccine or medication can cause side effects. Generally, most vaccines are well-tolerated. Most of the side effects experienced are minor such as sore arm or a low-grade fever. These side effects are a sign that the body is starting to build protection against a disease. The benefits of getting vaccinated outweigh the risk of the side effects. Serious side effects are extremely rare. According to the U.S. Department of Health and Human Services, 1-2 people out of 1 million may experience a severe allergic reaction.

Why should I get vaccinated?

Getting vaccinated is important for children and adults alike. Vaccines allow you to prevent a disease before it has a chance to get you sick. The infectious diseases that vaccines prevent once killed and harmed many infants, children, and adults.

Without these vaccines, children are at risk for getting seriously ill, suffering pain, disability, and possibly even death from diseases like measles and whooping cough. Measles can lead to serious complications like pneumonia and encephalitis (swelling of the brain). Measles is also highly contagious and can spread from person to person very quickly.

How do vaccines protect others that haven’t been vaccinated?

Vaccines not only protect the person who has been vaccinated but others in the community. Community immunity, or herd immunity, occurs when most of the population is immune to an infectious disease and provides indirect protection to those not immune to the disease.

Communities with lower vaccine rates are unable to achieve herd immunity. For example, the 2019 measles outbreak at Disneyland occurred because of

a lack of herd immunity. Community immunity protects everyone. It’s important because certain people cannot get vaccinated due to allergies or those with a weakened or failing immune system.

Watch the following graphic to see how community or herd immunity works.

What is the lifecycle of an immunization program?

An immunization program involves vaccinating a population to eradicate a disease. The following infographic shows why a disease that is nearly eradicated can begin to resurface.

When there is no vaccine for a disease, the number of people getting the disease is usually high. People worry about the disease and its complications.

1) After an immunization program for a disease begins, the number of people being vaccinated usually rises quickly.

2) At the same time, there will be some adverse reactions associated with the vaccine — almost always very few and very mild compared with illness and complications associated with the disease. (Note that this number remains fairly constant because it is a percentage of the number of people being vaccinated.)

3) As the number of people being vaccinated rises, the number of cases of disease drops. Eventually, the number of people getting the disease may approach, or even fall below, the small number of people having reactions from the vaccine.

4) At this point, most people may never have experienced the disease. They might start to worry less about the disease and more about possible side-effects from the vaccine. They might start to question whether the vaccine is necessary or safe, and some of them will stop getting immunized.

5) If enough people stop getting immunized, disease numbers will start to rise again, and there will be disease outbreaks.

6) People are reminded of how bad the disease can be, and turn back to immunization to avoid it. Vaccination numbers rise once more and disease numbers fall.

7) Ultimately, if enough people get immunized the disease will disappear altogether. So far this has happened once, with smallpox.

8) When there is no more disease, the immunization program can be stopped. The numbers of vaccinations and adverse reactions drop to zero.

Infographic and information courtesy of The Centers for Disease Prevention and Control

Why do we need to get vaccinated for diseases that have been eradicated in the United States?

Even though certain diseases have been eradicated in the United States, we still need to be vaccinated. Other countries may have not eradicated these diseases, and

international travelers could bring the disease into the United States.

For more information on the immune system, click the button below.