Vaccines

Vaccine

Definition

Vaccines are biological preparations that provide acquired immunity to a particular infectious disease. They typically contain an agent that resembles a disease-causing microorganism and is often made from weakened or killed forms of the pathogen, its toxins, or one of its surface proteins. The introduction of this agent into the body stimulates the immune system to recognize it as foreign, producing an immune response and creating “memory” cells that can respond more effectively if exposed to the actual pathogen in the future.

Key Aspects of Vaccines

1. Types of Vaccines:

• Live Attenuated Vaccines: These contain live pathogens that have been weakened so they cannot cause disease. Examples include the measles, mumps, rubella (MMR) vaccine and the oral polio vaccine.
• Inactivated or Killed Vaccines: These vaccines contain pathogens that have been killed or inactivated through heat or chemicals. Examples include the polio vaccine (injected) and the hepatitis A vaccine.
• Subunit, Recombinant, and Conjugate Vaccines: These vaccines use specific pieces of the pathogen (like proteins or sugars) to stimulate an immune response. For example, the hepatitis B vaccine is a subunit vaccine that contains only a part of the virus.
• Toxoid Vaccines: These contain inactivated toxins produced by bacteria. They stimulate immunity against the toxin rather than the bacteria itself. Examples include tetanus and diphtheria vaccines.
• mRNA Vaccines: These vaccines use messenger RNA to instruct cells to produce a protein associated with the pathogen, prompting an immune response. Notable examples include the Pfizer-BioNTech and Moderna COVID-19 vaccines.
• Viral Vector Vaccines: These use a harmless virus to deliver genetic material from the pathogen into cells, prompting an immune response. The Johnson & Johnson COVID-19 vaccine is an example.

Mechanism of Action:

• When a vaccine is administered, it triggers an immune response without causing the disease. The immune system recognizes the components of the vaccine as foreign and mounts a defense against them. This process involves producing antibodies and activating T-cells, which remain in memory for future encounters with the actual pathogen.

Immunization vs. Vaccination:

• Vaccination refers specifically to the act of administering a vaccine, while immunization is a broader term that encompasses both vaccination and the resulting protection from disease.

Community Immunity (Herd Immunity):

• When enough people in a community are vaccinated against a disease, it reduces its spread, providing indirect protection to those who are not vaccinated or cannot be vaccinated due to medical reasons.

Safety and Efficacy:

• Vaccines undergo rigorous testing for safety and efficacy before they are approved for public use. Monitoring continues even after approval to ensure ongoing safety.

Conclusion

Vaccines are a critical tool in public health for preventing infectious diseases and controlling outbreaks. They work by training the immune system to recognize and combat pathogens effectively, thereby providing individual and community protection.

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References

1. India Science, Technology & Innovation Portal. (n.d.). Types of Vaccine. Retrieved from ISTI Portal.
2. MedlinePlus. (2023). Vaccines | Immunization | Inoculation. Retrieved from MedlinePlus.
3. Wikipedia contributors. (2023). Vaccine. In Wikipedia, The Free Encyclopedia. Retrieved from Wikipedia.
4. History of Vaccines. (2022). Different Types of Vaccines. Retrieved from History of Vaccines.
5. Pfizer Thailand. (n.d.). Vaccine types | Covid-19 – Pfizerpro Thailand. Retrieved from Pfizerpro Thailand.