Vaccines are an important part of medical care because they can protect you from future illness or can make the severity of the illness much less serious. There are six types.

Vaccination is the process of protecting against pathogens (viruses, bacteria, and toxins) that cause disease by introducing a much smaller and safer component of the material (called antigens) into your body.

Vaccines come in several forms, such as injections, pills you take by mouth, liquids, and most recently, nasal sprays.

They teach your immune system to recognize and protect you from harmful germs or diseases by creating an immune response in your body. Some protect against viruses like the ones that cause the flu or COVID-19. Others target bacteria, like the ones that lead to tetanus or tuberculosis.

The immune response is how your body defends itself against harmful substances. This response:

  1. identifies the substance as foreign
  2. targets the substance for destruction
  3. helps your immune system remember the invader and to attack it again if it returns

The memory component, known as immunity, protects you against disease-causing germs in the future.

The practice of introducing a small amount of the substance that makes you sick to trigger an immune response dates back to the 10th century. The term “vaccine” dates back to the first smallpox vaccination in 1798. “Vaca” means cow in Latin. Samples of lesions from cowpox were used to vaccinate against smallpox.

There are six approved types of methods of vaccination in use today, and all are considered safe. They are:

  • inactivated vaccines
  • live-attenuated vaccines
  • subunit, recombinant, polysaccharide, and conjugate vaccines
  • toxoid vaccines
  • viral vector vaccines
  • messenger RNA (mRNA) vaccines

Read on to learn about the six types and how they’re different.

This type of vaccine uses a weakened (or attenuated) live form of the pathogen but without causing the disease. They are more likely to cause mild side effects than non-live vaccines. Typically, one or two doses is required to achieve long-lasting immune response. This is because they are very similar to the natural infection they protect against.

This type of vaccine requires refrigeration.

Examples include:

Inactivated vaccines use a version of the pathogen killed using heat or chemicals to trigger immunity. They typically don’t provide protection that’s as strong as live vaccines and require multiple doses (boosters) over time to get ongoing immunity.

Because they don’t use live antigens, they are considered safer for immunocompromised people.

This type of vaccine can be mass-produced quicker than live-attenuated vaccines.

Examples include:

These types of vaccines use specific pieces of a pathogen, such as its protein or carbohydrate, to produce an immune response. Because of this, they cannot make you sick or cause infection.

They are known to produce a strong immune response even though they’re considered safe for people with a compromised immune system. However, they may require several booster shots for sustained immunity.

Subunit vaccines can be made one of two ways: from the original pathogen, or from a different organism through genetic engineering (called a recombinant vaccine), to produce an antigen.

There are several subtypes.

Polysaccharide vaccines

Polysaccharide vaccines (encased in a layer of sugar) target an immune response to bacteria, producing an immune response against the surface of the bacteria. This type is ineffective in young children.

Conjugate vaccines

This type has a polysaccharide component, but in this case, the sugar is attached to a protein so your immune system will respond to the sugar on the bacteria better. This type of vaccine is effective in children under 2 and in people who are immunocompromised.

One example is meningitis.

Protein-based vaccines

This type causes a response to a protein on the surface of a virus or bacteria, or against a secreted toxin.

Examples include:

This type of vaccine uses an inactivated form of a toxin made by the pathogen to build immunity against its harmful side effects, rather than against the pathogen itself. As with some other types, continued booster injections may be needed to sustain protection against illness.

Because toxoid vaccines block the toxin’s effects but not bacterial colonization, proper wound care is essential, even after you are vaccinated.

Examples include:

Viral vector vaccines use one genetically modified virus to deliver instructions to your cells to create immunity against another virus. The immune response is usually strong, but booster shots may be needed to maintain immunity. Modified viruses have included:

  • adenovirus
  • influenza
  • measles
  • vesicular stomatitis virus (VSV)

Examples include Ebola and COVID-19 vaccines, while current research is looking at viral vector vaccine technology to create vaccines for Zika, flu, and HIV.

This type of vaccines uses messenger RNA, which instructs your cells how to make a protein of the pathogen, which in turn creates an immune response. This technology was crucial in the development of COVID-19 vaccines because they are quicker to produce.

They are also considered very safe because they do not include a live virus. However, boosters may be required to maintain immunity.

Examples include COVID-19 and respiratory syncytial virus (RSV). Researchers are now looking at mRNA vaccines for immunization against HIV, cancer, and seasonal flu.

Dispelling myths

One common myth that began during the COVID-19 pandemic that mRNA vaccines can alter your DNA, but this is false.

Researchers are continuing to create new types of vaccines. A current direction of study includes the possibility of DNA vaccines and recombinant vector vaccines.

DNA vaccines use DNA that creates specific antigens from a pathogen. Once injected into your body, the DNA for the pathogen Is reproduced until it’s recognized as an invader, leading to an immune response. Studies have shown immunization is long-lasting.

Recombinant vector vaccines, also known as platform-based vaccines, are intended to work as a natural infection to train your immune system to identify and attack pathogens. They reproduce a live virus that has been engineered to carry extra genes that make proteins your immune system needs to recognize and protect against the pathogen.

In the United States, there are six approved technologies to deliver vaccines to different groups of people, including young children and those with compromised immune systems. Approved vaccines are considered safe, and their benefits usually outweigh their potential side effects, or the effects of getting sick with the diseases they help prevent.

If you have concerns about a specific vaccine for yourself or your child, speak with a doctor about its benefits and side effects.