Explain Like I’m 65: "Vaccines"

Table of Contents:

  1. The Immune System
  2. Types of Vaccines
  3. Herd Immunity

Some people act like they know it all. Our new series Explain Like I’m 65 is for the rest of us. It will provide clear, digestible summaries to help seniors sort through the noise and get the factual information they need. From political buzzwords to household how-tos, we’re here to provide accessible guides and informative answers.

While there’s still no vaccine for COVID-19, scientists around the globe are hard at work developing one. This week, we’re taking a look at how vaccines help to boost the body’s defenses.

The Immune System

Before discussing vaccines, it’s important to understand how the body naturally fights off illnesses. When germs multiply inside the body, they spread infections and, unaddressed, cause illness. The body’s immune system staves off infection by producing a number of germ-fighting substances (like macrophages) to consume germs, and T-lymphocytes to attack cells that have already been infected.


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Vaccines work by simulating an infection to kickstart the immune system. Dead or weakened viruses and bacteria enter the body and lead the immune system to produce lymphocytes and other disease-fighting antibodies. This sometimes leads to minor symptoms, including fever and redness.

How do vaccines boost the immune system and eradicate disease.
How do vaccines help boost the immune system? Senior Life Advisor explains.

Types of Vaccines

Today, there are five primary types of vaccines:

  • Live Attenuated Vaccines: These vaccines introduce a weakened version of a virus or bacteria to the body. In its weakened state, the virus or bacteria will not infect a healthy immune system. Rather, the body will recognize the virus and learn how to combat it. Some common live vaccines include those for chickenpox and measles. Individuals with weakened immune systems typically cannot be vaccinated with live bacteria or viruses.
  • Inactivated Vaccines: Developing inactivated vaccines involves killing a virus or bacteria with extreme heat or chemicals. When the dead antigen is introduced to the body, the immune system studies it and learns to attack a live version in the future. Examples include the vaccines for polio and rabies. Individuals often require multiple shots to build or maintain their immunity.
  • Toxoid Vaccines: Bacterial diseases like tetanus and diphtheria release toxic substances into the body. To develop vaccines for these diseases, scientists chemically deactivate the toxins. The weakened toxins (called toxoids) enter the body and help the immune system learn to neutralize the natural, full-strength toxin.
  • Subunit Vaccines: These vaccines contain a part of a virus or bacteria rather than the entire antigen. Since subunits contain only partial germs, negative side effects are especially rare.
  • Conjugate Vaccines: Certain bacteria possess antigens with outer coatings made of polysaccharides. These sugar-like substances mask antigens and make them difficult for the immune system to recognize. Conjugate vaccines address these antigens by linking the polysaccharide coating to different antigens that the body already recognizes. The immune system learns to associate polysaccharides with these antigens and, ultimately, fights them off.

Herd Immunity

Vaccines don’t just boost individual immune systems, they help keep entire populations healthy. When a large enough chunk of a population is immunized against a disease, it becomes nearly impossible for an outbreak to occur. Eventually, the disease can die out entirely. This phenomenon is called “herd immunity,” and it’s a surefire way to protect those who can’t be vaccinated. If too many people forgo inoculation, herd immunity can go away and once-dormant diseases can return. This is part of why several vaccines are required for anyone who can get them.

Getting vaccinated represents both an individual and collective effort to promote public health. Until scientists develop a COVID-19 vaccine, we can all continue promoting public health by practicing safe social distancing and, when possible, adhering to stay-at-home orders. Learn more about what it means to help “flatten the curve.”