Why do we need vaccines?

What’s the difference?

According to the World Health Organization (WHO), these are the correct definitions:

• Vaccination uses vaccines to stimulate the body’s own immune system to protect a person against future infection or disease.
• Immunization is the process where a person is made immune or resistant to an infectious disease, typically by the administration of a vaccine.
• Inoculation, meanwhile, is often used interchangeably with vaccination or immunization. This term describes the introduction of a substance into the body to provide protection. The term was first coined in the 18th century to describe variolation, the use of a small amount of pus from someone with smallpox into the body of someone without it.

How vaccines work:

A pathogen is a bacteria, virus, parasite, or fungus that can attack us. Our body has many ways of defending itself against these microorganisms. It has physical barriers, such as skin, mucus, and cilia, that prevent them from getting in. But when they do, our immune system is there to protect us. 

Our immune system recognizes a part of a pathogen as a foreign substance or antigen. Then, it produces antibodies against this antigen, attacks it, and eliminates it. These antibodies are specific because they only attack this antigen. We have thousands of different antibodies in our bodies and that protects us against many diseases.

When our body produces antibodies against a pathogen, it also creates memory cells. These cells “remember” this microorganism so when our body is exposed to it again, the reaction is much faster and more effective than the first time. This response is specific and provides long term protection.

Getting vaccinated works the same way as when we are exposed to a disease. The difference is that these antigens do not cause the disease, but our immune system still creates antibodies as if we were exposed to the pathogen. This way, when we encounter the microorganism for the first time, we are ready to attack it in a more efficient way.

For example, when we are around a year old we get the varicella or chicken pox vaccine. Then, our immune system produces antibodies against this virus. If we are exposed to this pathogen, we get chicken pox, but it is a much milder version than if we had gotten it without being vaccinated.

Why most of us should get vaccinated:

There are people who cannot get vaccinated and are more likely to catch a preventable disease. For example, people who have had a severe allergic reaction to one of the components of a vaccine (i.e. Polyethylene Glycol (PEG) or Polysorbate are components of mRNA vaccines) or people who are immunosuppressed because they have a weakened immune system (i.e. medications or chronic illness).

When enough people in a community are vaccinated it reduces the number of people able to spread the infection within that community. This is how we have been able to eliminate (or nearly eliminate) diseases like polio, mumps, whooping cough, tetanus, and measles, which once killed millions of people.

That is why it is so important for the people who can get vaccinated to do so. This protects everyone, even those who have not been vaccinated yet or who cannot get vaccinated. This process is called herd immunity.