Microbes, or parts of them, are used in vaccines to stimulate the body's immune system, providing protection against future infections caused by that specific microbe. This stimulation creates immunological memory.
Types of Microbes Used in Vaccines
Vaccines employ various forms of microbes to trigger an immune response:
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Live, Attenuated Microbes: These are weakened versions of the disease-causing microbe. Because they are alive, they produce a strong and long-lasting immune response, often mimicking a natural infection without causing severe illness. An example is the measles, mumps, and rubella (MMR) vaccine.
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Inactivated Microbes: These vaccines use killed microbes. While they don't provide as strong or long-lasting immunity as live vaccines, they are safer for people with weakened immune systems. Multiple doses (booster shots) are often required. An example is the inactivated polio vaccine (IPV).
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Subunit, Recombinant, Polysaccharide, and Conjugate Vaccines: These vaccines use specific parts of the microbe, such as its surface proteins, sugars (polysaccharides), or toxins. Because they only contain specific components, they generally have a lower risk of side effects. Examples include the hepatitis B vaccine (subunit), the pneumococcal conjugate vaccine (conjugate), and the tetanus vaccine (toxoid).
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mRNA Vaccines: These are a newer type of vaccine that uses messenger RNA (mRNA) to instruct the body's cells to produce a harmless piece of the viral protein, which then triggers an immune response. An example is the COVID-19 vaccines developed by Pfizer-BioNTech and Moderna.
How Vaccines Work
Here's a simplified explanation of the process:
- Administration: A vaccine containing the microbial component is administered, typically by injection.
- Immune System Recognition: Immune cells recognize the microbial component as foreign.
- Immune Response: The immune system mounts a response, producing antibodies and activating immune cells (such as T cells) that can recognize and fight the microbe.
- Immunological Memory: Some immune cells become "memory cells." If the body encounters the actual microbe in the future, these memory cells will recognize it quickly and mount a rapid, effective immune response, preventing or lessening the severity of the disease.
Summary
In essence, vaccines use weakened, killed, or component parts of microbes to "teach" the immune system how to recognize and fight the real microbe, providing immunity without causing severe illness.
