Immunity is the body’s natural defense mechanism, protecting us from infectious diseases. This protection is usually indicated by the presence of antibodies, specialized protein molecules produced by the immune system to recognize and neutralize harmful organisms. Immunity is very specific to each pathogen, ensuring tailored responses for every infectious agent encountered.
Types of Immunity
- Active Immunity: This type of protection is produced by your own immune system. It is usually permanent, meaning once your body has been exposed to a pathogen, it remembers it, offering lifelong defense.
- Passive Immunity: In this case, protection is transferred from another person or animal, such as the immunity a baby receives from the mother through the placenta. However, this type of immunity is temporary and weakens over time.
How Vaccination Works
Vaccines mimic the process of natural infection, exposing the body to an antigen— a substance derived from a pathogen (bacteria or virus) that can trigger an immune response. These antigens are either live, inactivated, or components of the pathogen, such as proteins or polysaccharides. When the immune system encounters the antigen again in the future, it mounts a faster, stronger defense, often preventing illness altogether.
Types of Vaccines
- Killed Vaccines: These contain microorganisms that have been killed through chemical or heat treatment, rendering them unable to cause disease but still capable of stimulating an immune response. Examples include vaccines for polio and rabies.
- Attenuated Vaccines: These vaccines contain live microorganisms that have been weakened under laboratory conditions to lose their virulence. They provoke a robust immune response without causing severe disease. Vaccines for measles, mumps, and rubella are examples.
- Toxoid Vaccines: Some bacteria release toxins that make you sick. Toxoid vaccines are made from inactivated toxic compounds of the bacteria, which help the immune system recognize and fight these toxins. Tetanus and diphtheria vaccines fall into this category.
- Subunit Vaccines: Rather than using the whole pathogen, subunit vaccines use specific protein fragments of the microorganism to trigger an immune response. An example is the Hepatitis B vaccine, which is made from surface proteins of the virus.
- Conjugate Vaccines: Some bacteria have outer coats made of polysaccharides that are not very effective at triggering the immune system. Conjugate vaccines combine these polysaccharides with proteins (such as toxins) to improve immune recognition. The Haemophilus influenzae type B (Hib) vaccine uses this technique.
Vaccination is a key player in public health, protecting individuals and communities from diseases that once claimed millions of lives. By understanding how immunity works and the different types of vaccines available, we can appreciate the science behind the shots that safeguard our health.
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