1. Immunity and How Vaccines Work

Immunity and How Vaccines Work.

Contents. 1. Introduction 2. Types of Immunity 3. Active Immunity 4. Antibody-Mediated Immunity 5. Cell-Mediated Immunity 6. Passive Immunity 7. How Vaccines Work 8. Inactivated and Live Vaccines 9. Vaccine Production 10. Vaccine Excipients 11. Population Immunity 12. Vaccine Failure 13. Immunoglobulins.

[Audio] In simple terms, immunity is how the body defends itself against germs and infections. The body has two main ways to protect itself:Innate Immunity (Non-Specific) – This is the body's first line of defense, like skin, mucus, and stomach acid. It fights off all germs in the same way and doesn't change over time.Acquired Immunity (Specific) – This is the body's smart defense system. It learns to recognize and remember specific germs (like viruses or bacteria) and fights them more effectively if they come back..

[Audio] Innate (Non-Specific) Immunity – This is the natural protection you're born with. It includes:Physical barriers like skin and mucus that block germs.Chemical barriers like stomach acid and skin oils that kill germs.Immune cells that attack and destroy invaders.Acquired (Specific) Immunity – This is the body's learned defense system that targets specific germs.Active Immunity – Your body makes its own protection after being exposed to a germ or vaccine.Passive Immunity – You get temporary protection from outside sources, like antibodies from a mother's milk or an injection..

[Audio] Active immunity is your body's own defense system that fights off infections. It lasts a long time because your immune system remembers how to fight specific germs.Your body creates its own protection when exposed to a germ or a vaccine.Vaccines train your immune system to fight diseases without making you sick.There are two ways your body fights infections:Antibody-Mediated Immunity – Your body makes special proteins (antibodies) that attack germs.Cell-Mediated Immunity – Special immune cells fight and destroy infected cells.Think of it like learning to ride a bike – once your body learns how to fight a disease, it remembers for a long time! 🚴‍♂️💪.

[Audio] Your body has B cells, a type of immune cell that helps fight infections. When B cells detect a harmful germ (antigen), they multiply and transform into plasma cells.These plasma cells produce antibodies, which act like tiny soldiers that:Neutralize toxins (stop harmful substances from damaging your body).Block germs from attaching to or entering your cells.Prevent viruses from making copies of themselves.Help destroy infected cells by signaling other immune cells to attack.Think of antibodies like security guards—they recognize and stop harmful invaders before they cause trouble! 🦠🚫🔬.

[Audio] Your immune system has T cells, which help control and fight infections in different ways:T-helper cells: These act like team leaders, signaling other immune cells to respond when there's an infection.T-suppressor cells: These work like brakes, preventing the immune system from overreacting and attacking healthy cells.Cytotoxic T cells: These act like assassins, directly killing infected cells to stop the spread of harmful invaders.Together, T cells regulate, boost, and control your body's defense system to keep you safe! 🔬🛡️.

[Audio] Passive immunity is when you receive ready-made antibodies instead of your body making them. This happens in two main ways:From Mother to Baby: A mother passes protective antibodies to her baby through the placenta before birth, helping protect the baby from infections like measles and tetanus for the first few months.Through Blood Products: Antibodies can also be transferred through blood transfusions or immunoglobulin injections to give short-term protection.However, passive immunity is temporary, lasting only a few weeks or months because the body doesn't make its own antibodies..

[Audio] Vaccines teach your body how to fight infections before you actually get sick. They help your immune system recognize harmful germs so that if you get exposed later, your body can fight them off quickly. Types of Vaccines: Traditional Vaccines Made from weakened or killed germs. Some use small parts of the germ instead of the whole thing. Example: Flu vaccine, measles vaccine. Newer VaccinesUse a harmless virus to deliver the germ's information to your body. Your immune system then learns how to fight the real germ. Example: Some Ebola and COVID-19 vaccines. mRNA & DNA Vaccines These vaccines do not contain actual germs.Instead, they give your body instructions to make a tiny, harmless part of the germ. Your immune system recognizes this part and learns how to fight it. Example: COVID-19 vaccines (Pfizer & Moderna use mRNA).Are They Safe? mRNA vaccines break down quickly in your body – they do not stay forever. DNA vaccines do not change your DNA – they just help your body make immunity. Why Vaccines Are Important:✅ Prevent serious diseases✅ Protect people around you✅ Help stop outbreaks Vaccines train your body to fight infections before they can make you sick!.

[Audio] Inactivated Vaccines – Simple Explanation These vaccines use killed (inactivated) bacteria or viruses, meaning they cannot cause the disease. Because they use a weaker form of the germ, the body needs multiple doses or booster shots to build long-lasting immunity. Examples: Polio vaccine (IPV) Hepatitis A vaccine Rabies vaccine ✅ Safe for people with weakened immune systems ✅ Cannot mutate back into a harmful form ❌ May require booster shots over time These vaccines train your body to recognize and fight the germs without the risk of infection! Live Attenuated Vaccines – Simple Explanation These vaccines contain a weakened (but live) form of the virus or bacteria. Because the germ is still alive but too weak to cause disease, the immune system builds strong, long-lasting protection—often with just one or two doses. Examples: Measles, Mumps, and Rubella (MMR) vaccine Chickenpox (Varicella) vaccine Yellow fever vaccine Oral polio vaccine (OPV) ✅ Strong and long-lasting immunity ✅ Often requires fewer doses ❌ Not recommended for people with weak immune systems.

[Audio] Vaccines are made by growing the virus or bacteria in special environments, like eggs (for the flu) or cells from animals or humans. These environments provide nutrients and growth factors, some of which come from animal sources, such as blood serum, milk, or meat extracts. These substances are used in the early stages of making the vaccine but should not be in the final product, or only in very small amounts. In some cases, animal enzymes, like trypsin (from pigs), are used to hep grow the virus. However, these enzymes are removed during later steps in the manufacturing process, ensuring they don't end up in the final vaccine. Trypsin is also used in making other medical products, like insulin. Here are some examples of the materials and processes used in vaccine production: Eggs (Influenza vaccine): The flu virus is often grown in chicken eggs, which provide nutrients for the virus to grow. This is one of the most common methods for producing flu vaccines. Cell Lines (Measles, Mumps, Rubella vaccines): These vaccines are grown in cells from animals, such as monkeys or human cells, to cultivate the virus needed for the vaccine. Animal-derived substances: Serum (from cows or horses): Used in the early stages to provide growth factors for the virus to thrive. Gelatin: Derived from animals (usually pigs or cows), it is used as a stabilizer in some vaccines. Milk and milk derivatives: Sometimes used in the growth medium for virus production, especially in the early stages. Trypsin (from pigs): This enzyme is used to help the virus grow in cell cultures. It's a common ingredient in the production of vaccines, but it is removed during the final stages to ensure the vaccine doesn't contain any traces. Insulin and Heparin: These medical products are also made using similar animal-derived substances, such as trypsin, during their production processes. These examples show how vaccines are made using various biological materials, but all animal-derived ingredients are typically removed or reduced to minimal traces by the time the vaccine is ready for use..

[Audio] Vaccines are complex, and a variety of ingredients are used to ensure they are safe and effective. These ingredients, called excipients, help maintain the quality of the vaccine.Here are some examples of excipients in vaccines:Gelatine: This is an animal product used in many vaccines as a stabilizer, which helps keep the vaccine safe and effective during storage. It's a purified form of gelatine, broken down into small molecules called peptides. Gelatine is also used in many medicines and capsules.Adjuvants: These are special chemicals that help boost the body's immune response to the vaccine.Aluminium salts (like aluminium hydroxide or phosphate) are the most common adjuvants. They've been used safely in vaccines for over 70 years. They help the vaccine stay at the injection site long enough for the immune system to respond. They are especially good at stimulating humoral immunity (the immune system's response involving antibodies).MF59: This newer adjuvant is made from squalene, an oil extracted from sharks' livers. It is used in flu vaccines for the elderly to improve protection against the flu. It's also being considered for use in COVID-19 vaccines.These excipients and adjuvants play an important role in making sure vaccines are both effective and safe..

[Audio] The main goal of vaccination is to protect the person who gets the vaccine. But vaccines also help prevent the spread of infection to others, which reduces the risk for people who are not vaccinated. This is especially important for those who cannot get vaccinated, such as babies too young for certain vaccines.This idea is called herd immunity (or population immunity). For example, babies under one year old are protected from a type of meningitis (serogroup C meningococcal infection) because teenagers are vaccinated. Teenagers are less likely to carry the bacteria, so the chance of spreading it to others is lower.When enough people are vaccinated, it can even lead to the elimination of certain diseases from a country or region. For example, smallpox was completely eradicated in 1980, and polio is close to being eradicated worldwide.However, if vaccination rates drop, these diseases could come back. This shows how important it is to keep vaccination rates high to protect the entire population..

[Audio] No vaccine guarantees 100% protection, so some people may still get infected even after being vaccinated. There are two types of vaccine failure: primary failure and secondary failure. Primary failure happens when a person doesn't respond well to the vaccine in the first place. As a result, they can still get infected after vaccination. For example, 5–10% of children may not respond to the measles part of the MMR vaccine (measles, mumps, rubella), meaning they are at risk for measles. To help protect these children, a second dose of the vaccine is given, usually before they start school. Secondary failure happens when a person initially responds well to the vaccine but the protection weakens over time. For example, the protection against whooping cough (pertussis) from the vaccine is strong after the first three doses, but it can decrease as a child grows older. To boost protection, a fourth dose (called a booster) is given when the child reaches school age. Even when vaccines don't fully prevent illness, people who do get infected are often less likely to experience serious complications compared to those who were never vaccinated..

[Audio] Passive immunity is a type of protection given by injecting human immunoglobulin (antibodies), which temporarily boosts an individual's ability to fight off a specific infection. This protection kicks in within a few days but usually only lasts a few weeks. Human Normal Immunoglobulin (HNIG) is made from the pooled plasma of blood donors and contains antibodies against common infections. It's used to protect people with weak immune systems, like children at risk of measles, or individuals exposed to hepatitis A. Specific immunoglobulins are available for infections like tetanus, hepatitis B, rabies, and chickenpox. These immunoglobulins have a higher concentration of antibodies for the specific infection they target. They are made from the blood of donors who: Are recovering from the specific infection, Have been recently vaccinated against the infection, or Have been screened and found to have high levels of antibodies for that infection. This form of immunity is temporary but can be critical for immediate protection after exposure to certain diseases..