How Vaccines Actually Train Our Immune System.

Vaccination is a simple, safe, and effective way of protecting you against harmful diseases before you come into contact with them. It uses your body's natural defenses to build resistance to specific infections and makes your immune system stronger.

We’ve all heard that, right?

But what exactly are vaccines, and how did they come into existence?

Vaccines are injections (shots), liquids, pills, or nasal sprays that you take to teach your body's immune system to recognize and defend against harmful germs. For example, there are vaccines to protect against diseases caused by COVID-19.

But why do we feel the need to get our children vaccinated at a young age?

Vaccines protect us throughout life and at different ages, from birth to childhood, as teenagers, and into old age. In most countries, you will be given a vaccination card that tells you what vaccines you or your child have had and when the next vaccines or booster doses are due. It is important to make sure that all these vaccines are up to date.

If we delay vaccination, we are at risk of getting seriously sick. Waiting until we think we may be exposed to a serious illness, like during a disease outbreak, might not leave enough time for the vaccine to work or to receive all the recommended doses.

If you have missed any recommended vaccinations for yourself or your child, talk to your healthcare worker about catching up.

But then again, we need to look at the bigger picture and determine whether or not vaccines have side effects.

Let’s dive deeper into that.

Like any medicine, vaccines can cause mild side effects such as a low-grade fever, or pain or redness at the injection site. These mild reactions usually go away within a few days on their own.

Severe or long-lasting side effects are extremely rare. Vaccines are continually monitored for safety to detect rare adverse events.

For the most part, these side effects are minor, such as a sore arm or low-grade fever, and they go away within a few days. Listed below are vaccines licensed in the United States and the side effects that have been associated with each of them.

Staying Up to Date with Recommended Vaccines

Staying up to date with vaccinations is critical to help protect infants and other children against potentially life-threatening diseases. According to the Centers for Disease Control and Prevention (CDC), among children born between 1994 and 2018, vaccination will prevent an estimated 419 million illnesses, 26.8 million hospitalizations, and 936,000 deaths over their lifetimes. Children can be protected against 14 serious childhood diseases through vaccination, including hepatitis, influenza (flu), tetanus, and polio. New prevention and treatment interventions are in development for respiratory syncytial virus (RSV), which is the leading cause of hospitalization in US infants, resulting in 58,000 hospitalizations and an estimated 100 to 500 deaths among children younger than age five each year.

So, What Is the Immune System Exactly?

The immune system is a complex network of organs, cells, and proteins that defends the body against infection while protecting the body’s own cells.

The immune system keeps a record of every germ (microbe) it has ever defeated so it can recognize and destroy that microbe quickly if it enters the body again.

White blood cells, antibodies, and memory cells are crucial components of the body's immune system. White blood cells, particularly lymphocytes, identify and target pathogens. Antibodies, produced by lymphocytes, bind to and neutralize these pathogens, making them easier to destroy. Memory cells, also produced by lymphocytes, "remember" past infections, allowing for a faster and more effective response upon re-exposure to the same pathogen.

What Are Vaccines Made Of?

Vaccines work by safely introducing your body to a fake or weakened version of a disease, allowing your immune system to learn how to fight it without you actually getting sick. The main ingredient in a vaccine is an antigen, which is the part of the virus or bacteria that your immune system recognizes.

These antigens can come in different forms. Some vaccines use whole, weakened pathogens like those used for MMR. Others use inactivated (killed) pathogens like some flu shots. Still others use only specific parts of the pathogen, like proteins or sugars, which are called subunit, recombinant, or polysaccharide vaccines. Some vaccines, such as those for tetanus and diphtheria, use inactivated toxins called toxoids.

Newer types of vaccines include mRNA vaccines, which use genetic instructions to teach your cells to make a harmless viral protein. Viral vector vaccines use a modified, harmless virus to deliver similar instructions.

Besides the antigen, vaccines also contain other ingredients. Adjuvants help boost your immune response. Stabilizers keep the vaccine effective during storage. Preservatives prevent contamination in multi-dose vials. Diluents are used to prepare the vaccine for injection.

When you get a vaccine, your immune system recognizes these antigens as foreign and starts producing antibodies and memory cells. These memory cells "remember" the specific antigen. So, if you encounter the real disease in the future, your body can quickly launch a strong immune response and protect you from getting seriously ill.

Types of Vaccines

Vaccines come in several distinct types, each designed to safely introduce antigens and train the immune system.

Live-attenuated vaccines use a weakened, live version of the pathogen that can replicate but not cause disease. These vaccines provide strong, long-lasting immunity and are used for diseases like measles, mumps, rubella (MMR), chickenpox, and yellow fever.

Inactivated vaccines contain whole pathogens that have been killed. These vaccines, like some for polio and influenza, do not replicate and often require multiple doses to build effective immunity.

Subunit, recombinant, or polysaccharide vaccines use only specific, purified parts of the pathogen, such as proteins or sugars. This approach is used for hepatitis B, HPV, and some pneumococcal vaccines.

Toxoid vaccines use inactivated bacterial toxins to teach the immune system to neutralize harmful substances produced by bacteria. Examples include diphtheria and tetanus vaccines.

Newer technologies include mRNA vaccines, such as some COVID-19 vaccines, which provide genetic instructions for your cells to produce a harmless viral protein. Viral vector vaccines, used for Ebola and some COVID-19 vaccines, employ a modified, harmless virus to deliver similar genetic instructions.

References

WHO – What is Vaccination?

CDC – Vaccines for Your Children

CDC – Vaccine Safety

CDC – How Vaccines Work

CDC – Types of Vaccines

WHO – Immunization Coverage

CDC – mRNA Vaccines

CDC – Viral Vector Vaccines