C3.2.16 Vaccines and immunization Notes

Vaccines and Immunization

1. Imagine a world without vaccines.
2. Diseases like smallpox, polio, and measles would still be rampant, causing widespread suffering and death.
3. Vaccines have transformed global health, but how do they work?

What Is a Vaccine?

1. A vaccine is a biological preparation designed to stimulate the immune system to recognize and fight specific pathogens.
2. It does this by introducing antigens or genetic material (DNA or RNA) that codes for antigens.

Types of Vaccines

1. Live Attenuated Vaccines
   1. Contain a weakened form of the pathogen.
   2. Stimulate a strong immune response.
   3. Examples: Measles, mumps, and rubella (MMR) vaccine.
2. Inactivated Vaccines
   1. Contain a killed form of the pathogen.
   2. Safer for people with weakened immune systems.
   3. Examples: Polio and influenza vaccines.
3. Subunit Vaccines
   1. Contain specific antigens (usually proteins) from the pathogen.
   2. Focus the immune response on key targets.
   3. Examples: Hepatitis B and HPV vaccines.
4. Nucleic Acid Vaccines (DNA or RNA)
   1. Contain genetic instructions for making an antigen.
   2. Human cells produce the antigen, triggering an immune response.
   3. Examples: COVID-19 vaccines like Pfizer/BioNTech (mRNA).

How Vaccines Work

1. Introducing the Antigen

Vaccines introduce antigens or genetic material coding for antigens into the body.

2. Activating the Immune System

1. Recognition: Antigens are detected by helper T-lymphocytes.
2. Activation: Helper T-cells activate B-lymphocytes, which produce antibodies specific to the antigen.
3. Response: Antibodies neutralize the antigen, and phagocytes engulf and destroy it.

3. Creating Memory Cells

1. Vaccines stimulate the production of memory B-cells and memory T-cells.
2. These cells "remember" the antigen, enabling a rapid and strong response if the pathogen is encountered again.

The Importance of Vaccines

Vaccines are essential for preventing diseases and controlling the spread of infections. Here’s why vaccines are so crucial:

1. Disease Prevention

1. Vaccines prevent diseases by stimulating the immune system without causing the illness.
2. Vaccination reduces the number of people who can get sick and, in turn, reduces transmission within the community.

2. Activation of Herd Immunity

1. Herd Immunity is when a large portion of a population becomes immune to a disease, either through vaccination or prior infection.
2. When enough people are immune, the disease cannot spread easily because there are fewer people to infect.

3. Eradication of Diseases

1. Vaccination programs have been crucial in the eradication or significant reduction of deadly diseases like smallpox and polio.
2. Ongoing vaccination efforts aim to eliminate diseases like measles and rubella.

COVID-19 Vaccination Efforts

1. The COVID-19 vaccine rollout has been crucial in controlling the pandemic. Vaccines have drastically reduced severe cases and hospitalizations.
2. Widespread vaccination has also contributed to reducing transmission of the virus and improving herd immunity.