Medical Intervention Vaccine

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Live Attenuated Vaccine

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A live attenuated vaccine uses the whole virus, but it has been weakened so it cannot cause disease in healthy people. It is made by growing the virus many times in embryo (usually chicken) cells, causing it to adapt to those cells and lose its ability to infect humans. After injection, the weakened virus triggers the immune system, which attacks it before it can infect human cells. This type of vaccine works very well because the body sees the entire virus and responds as if it were a real infection, creating a strong and long-lasting immune response with high T-cell activity. An example is the MMR vaccine.

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Inactivated Vaccine

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An inactivated vaccine uses the whole pathogen, but it has been killed so it cannot replicate. It is made by heat or chemical treatment that destroys the pathogen’s ability to reproduce. After injection, the immune system recognizes and attacks the pathogen before it can cause illness. This type of vaccine produces a weaker immune response and shorter-lasting immunity, so booster shots are often needed and it is commonly used for seasonal viruses. An example is the influenza (flu) vaccine

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Protein Subunit Vaccine

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A protein subunit vaccine uses only a specific part of the virus, usually the spike or surface protein. It is made either by growing the virus and extracting the spike proteins or by using DNA technology to replicate the spike protein many times. After injection, the spike proteins trigger the immune system to recognize and destroy them, but because the immune response is relatively weak, an adjuvant is added to greatly increase the response. This type of vaccine is the second strongest and produces good immunity without using the whole virus. An example is the HPV vaccine.

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MRNA/DNA Vaccine

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An mRNA/DNA vaccine uses only the genetic instructions from the virus, specifically the mRNA that codes for the spike protein, which is easier to work with and more stable than the whole virus. It is made by isolating this section of mRNA and replicating it millions of times in a lab. After injection, the mRNA enters human cells and instructs them to produce the viral spike protein, which triggers the immune system to respond. This type of vaccine produces a very strong and immediate immune response with high CD4 and CD8 T-cell activity. An example is the COVID-19 vaccine.

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Viral Vector Vaccine

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A viral vector vaccine uses genetic material from a virus, similar to mRNA vaccines, but it is delivered differently. The genetic instructions for making the spike protein are taken from the virus and copied many times in a lab. After injection, this genetic material is carried into human cells by a harmless adenovirus, which helps deliver the instructions into the cells. The human cells then produce the spike protein, triggering an immune response. This vaccine produces a strong immune response, though it is slightly less powerful than an mRNA vaccine. An example is the Ebola vaccine.

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Toxoid Vaccine

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A toxoid vaccine is used against bacterial diseases by training the immune system to recognize the toxin the bacteria produces rather than the bacteria itself. It is made by chemically inactivating the toxin so it cannot cause harm. After injection, the immune system responds to the inactive toxin and learns to neutralize it before it can damage human cells. Toxoid vaccines work well but usually require booster shots and act quickly. An example is the Tdap vaccine.