Published On: Wed, Sep 7th, 2022

6 Types of Vaccines and How They Work

Infectious diseases have existed for millions of years. But, humanity learned how to prevent them only recently – in fact, the first known vaccine was developed only in 1798. It contained a small strain of cowpox and was used to inoculate people from chickenpox. For a long time, vaccines were based on weaker forms of viruses to produce antibodies.

They were made so as not to make people utterly sick or ideally have no symptoms at all. The first attenuated human vaccine was created in a lab for the rabies virus. There are several ways of making vaccines. Some of them contain small portions of viruses that were altered and weakened enough not to make people sick. Today you’ll learn all about them.

CDC/ Debora Cartagena

Live, Attenuated Vaccines

There are several ways of producing this type of vaccine. The most common include putting a virus through several animal embryos or cell cultures. Usually, a series of chicken embryos are used to make the virus safe. Each time it becomes less able to replicate in human cells.

Sometimes it takes putting a virus through 200 cell cultures or embryos. The diluted form of the disease doesn’t spread as much through the human cells and can be used in a vaccine. Basically, the method puts viruses through non-human hosts. As a result, the immune system recognizes and attacks the virus, but the infection can’t replicate well in the cells.

Even if the person does get sick, their immune system will do a better job fighting the disease. The problem with this method is that the vaccine virus can return to its original form. Because of this, people might get a more virulent strain of the disease. That’s why when working on them, vaccinologists take possible mutations into account.

Killed or Inactivated Vaccines

This is an alternative to attenuated or live vaccines. They are made by inactivating a pathogen through chemicals like formaldehyde or formalin. Another method involves heat. This way, the pathogen can’t replicate but is kept inert for the immune system to fight it. Because of this, they can’t mutate into more virulent forms that make people sick. The first inactivated vaccines include:


  • Cholera
  • Plague
  • Typhoid


But, the downside is they provide shorter protection in comparison with live vaccines. Because of this, people need booster shots for long-term immunity. The most known inactive vaccines are used for seasonal flu and polio. Both are used to build immunity in children. If the vaccine is not activated properly, it can result in infectious particles getting into the bloodstream.

  1. mRNA Vaccines

This is the newest type of vaccine that was developed to combat the COVID-19 pandemic. It was made as part of a global race for a vaccine for the SARS CoV-2 virus. The US spent billions of dollars on scientific research as part of the “Operation Warpspeed” program. Because of the virulent nature of the disease, research was conducted faster than usual.

As a result, two vaccines based on mRNA technology were approved for emergency use by the end of the year. They use mRNA coated in a lipid sphere. When the vaccine is injected into the body, the immune cells unravel the vaccine particles and release the mRNA. It gives the cells code to generate a protein that’s like the one found on the coronavirus’ surface.

The immune system then produces that protein to other cells. This triggers an immune response. It includes activation of specialized cells and antibody production. Both of them work to kill coronavirus cells containing the spike protein and infected body cells.

Subunit and Conjugate Vaccines

Both vaccines contain small pieces of pathogens. Subunit vaccines use them to get a response from the immune system. Scientists do this by isolating specific pathogen proteins that play the role of antigens. Short-form flu and pertussis vaccines are of the subunit type. Another form of such inoculations is made through genetic engineering.

The coding of a vaccine protein is introduced to another virus or cell culture. The vaccine proteins are created when the producer cell metabolizes, or the carrier virus reproduces. When injected into the human body, the immune system will recognize the protein and give protection against the virus. US immunologists use this method for the Hepatitis B vaccine.

Human papillomavirus is another disease that’s treated with genetically engineered vaccines. There are several versions of this immunization. One is used for protection against two strains of the virus, while the other is against four. All are made through the isolation of a single viral protein.


While some bacterial diseases are caused by pathogens, others occur from the toxins they produce. One of such viruses is tetanus. Its bacterias don’t produce symptoms. Instead, they are caused by a neurotoxin called tetanospasmin. Vaccines used for this type of disease inactivate such toxins. This is done through heat or chemicals like formalin.

It’s the same principle that’s used in inactive or killed vaccines. Such vaccines are called toxoids. They are often considered the same as immunizations that inactivate viruses. But, sometimes, they’re given a separate category. That’s done to emphasize that they kill toxins instead of bacteria.

Viral Vector

Another COVID-19 vaccine created during the pandemic was released in early 2021. It used a hollowed-out version of the simian adenovirus with an mRNA coding of coronavirus spike added inside it. As with mRNA vaccines, the component is introduced into the immune system after the cells recognize the adenovirus. The immune cells then create the spike protein.


There are still diseases that don’t have a vaccine for them. But, the progress made in the past decade shows progress. With proper funding, humanity can beat infectious diseases that plagued it for hundreds of years. Polio has become a thing of the past since 1979. Maybe one day, people will be free of HIV and other viruses that rampage through the planet.

Author: Mike Walker

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