Public Health Lectures PDF

 Acquired immunity Acquired immunity can be active or passive. 1. Active immunity The stimulation of the immune system to produce antibodies against a particular infectious agent.  Active immunization results from the development of antibodies in response to an ant...

 Acquired immunity Acquired immunity can be active or passive. 1. Active immunity The stimulation of the immune system to produce antibodies against a particular infectious agent.  Active immunization results from the development of antibodies in response to an antigen, as from exposure to an infectious disease or through vaccination. Active immunization types i. Naturally acquired active immunity: is immunity that comes from infections encountered in daily life. ii. Artificially acquired active immunity: It is stimulated by initial exposure to specific foreign macromolecules through the use of vaccines to artificially establish a state of immunity.  2- Passive immunity is developed by antibodies that are produced outside and then introduced into the body. Passive immunity is acquired when antibodies are introduced into the body from an external source to provide a quick response to the infection.  Passive immunity results from the transmission of antibodies , as from mother to fetus through the placenta or by the injection of antiserum Passive immunity types i. Naturally acquired passive immunity: refers to antibodies that transferred from mother to fetus across the placenta and to newborn in colostrum and breast milk during the first few months of life. ii. Artificially acquired passive immunity: is transfer of antibodies that are formed by an animal or a human to an individual to prevent or treat infection. What is the loaned antibodies??? Immunization is the general term for all types of the processes whereby a person is made resistant to a disease. Immunization is a process by which a person becomes protected against a disease An individual can acquire immunity either passively or actively and thus immunization may be active or passive immunization. Immunization is a global health and development success story, saving millions of lives every year.  Vaccination Artificial Active Immunization Adaptive immunity Immune response What is Active Immunization? Active Immunization is the process whereby a person naturally acquires or is induced to acquire immunity or resistance to an infectious disease. In active immunization, the immune system is stimulated to produce antibodies against a particular infectious agent and thus the immune system of the individual is actively involved in the process. It may arise naturally, such as when an individual is exposed to an antigen or pathogen. For example, an individual who recovers from a first case of measles is protected from further infection by the measles-causing virus, because the virus stimulates the immune system to produce antibodies that specifically recognize and neutralize the pathogen the next time it is encountered. However, active immunization also can be conferred artificially by means of vaccines. Vaccines contain a nontoxic antigen preparation that infers protective immunity by inducing a memory response to an infectious microorganism. This results in immunity which may either be antibody - mediated immunity and/or cellular mediated immunity.  Vaccines consist of microbial products with adjuvant which do not cause infection under normal conditions but rather provide a long - term immunological protection against the specific microbe. Depending upon the type of disease, a vaccine may contain live attenuated, killed microorganisms, parts , or products from them capable of stimulating a specific immune response comprised of protective antibodies and T cell immunity. The purpose of vaccination is to ensure that a large enough number of antibodies and lymphocytes capable of reacting against a specific pathogen or toxin are available before exposure to this pathogen.  Artificial active immunization can be induced via two different routes : Systemic immunization which involves injecting the vaccine subcutaneously or intramuscularly into the deltoid muscle. Examples include systemic vaccines for measles, mumps and rubella, and against Pneumococcus, Meningococcus and Haemophilus infections. Mucosal immunization which involves on the mucosal route as the site of choice for immunization either orally or through the nasal associated lymphoid tissue (NALT) such as the oral immunization against Polio. Although not commonly in practice, recent vaccination approaches have focused on this route. Active immunization is mostly performed as a prophylaxis measure. Some infections in which active immunization is performed include Hepatitis A infection, Influenza, Measles, Mumps, Rubella, Yellow fever etc. Advantages The protection offered by active immunization is long-lived since it leads to the formation of long-lasting memory immune cells. Active immunization may be reactivated quickly by a recurrence of the infection or by revaccination. Drawbacks The protective response takes time to establish ranging from few days to weeks which makes it inefficient as a post exposure remedy. Since active immunization is dependent on the individuals’ immune responses, it may not be suitable for protection of immuno- compromised or immuno-deficient individuals. Vaccine Types There are several different types of vaccines. Each type is designed to teach the immune system how to fight off certain kinds of pathogens and the serious diseases they cause. When scientists create vaccines, they consider: How the immune system responds to the specific pathogens. Who needs to be vaccinated against the pathogen. The best technology or approach to create the vaccine. Based on a number of these factors, scientists decide which type of vaccine they will make. There are several types of vaccines, including: Inactivated vaccines Live-attenuated vaccines Messenger RNA (mRNA) vaccines Subunit, recombinant, polysaccharide, and conjugate vaccines Toxoid vaccines Viral vector vaccines Inactivated vaccines Inactivated vaccines use the killed version of the germ that causes a disease. Inactivated vaccines usually don’t provide immunity (protection) that’s as strong as live vaccines. So you may need several doses over time (booster shots) in order to get ongoing immunity against diseases. Inactivated vaccines are used to protect against: Hepatitis A Flu Polio Rabies Live-attenuated vaccines Live vaccines use a weakened form of the pathogen that causes a disease. Because these vaccines are so similar to the natural infection that they create a strong and long-lasting immune response. Just 1 or 2 doses of most live vaccines can give a lifetime of protection against a pathogen and the disease it causes. Live vaccines also have some limitations. For example: Because they contain a small amount of the weakened live virus, some people should talk to their health care provider before receiving them, such as people with weakened immune systems, long-term health problems, or people who’ve had an organ transplant. This type of vaccine needs to be kept cool, so it doesn’t travel well. That means this vaccine can’t be used in countries with limited access to refrigerators. Live vaccines are used to protect against: Measles, mumps, rubella (MMR combined vaccine),Rotavirus Smallpox, Chickenpox ,Yellow fever Messenger RNA vaccines (mRNA vaccines) mRNA vaccines make proteins in order to trigger an immune response. mRNA vaccines have several benefits compared to other types of vaccines, including shorter manufacturing times and, no risk of causing disease in the person getting vaccinated because they do not contain a live virus mRNA vaccines are used to protect against: COVID-19 Subunit, recombinant, polysaccharide, and conjugate vaccines Subunit, recombinant, polysaccharide, and conjugate vaccines use specific pieces of the pathogen —like its protein, sugar, or capsid. Because these vaccines use only specific pieces of the pathogen , they give a very strong immune response that’s targeted to key parts of the pathogen. They can also be used on almost everyone who needs these vaccines , including people with weakened immune systems and long-term health problems. One limitation of these vaccines is that the individual may need booster injections to get ongoing protection against diseases. These vaccines are used to protect against: Hib (Haemophilus influenzae type b) disease Hepatitis B HPV (Human papillomavirus) Whooping cough (part of the DTaP combined vaccine) Pneumococcal disease Meningococcal disease Shingles Toxoid vaccines Toxoid vaccines use a toxin (harmful product) made by the pathogen that causes a disease. They create immunity to the parts of the pathogen that cause a disease instead of the pathogen itself. Like some other types of vaccines, you may need booster injections to get ongoing protection against diseases. Toxoid vaccines are used to protect against: Diphtheria Tetanus Viral vector vaccines For decades, scientists studied viral vector vaccines. Some vaccines recently used for Ebola outbreaks have used viral vector technology, and a number of studies have focused on viral vector vaccines against other infectious diseases such as Zika, flu, and HIV. Scientists used this technology to make COVID-19 vaccines as well. Viral vector vaccines use a modified version of a different virus as a vector to deliver protection. Several different viruses have been used as vectors, including influenza, vesicular stomatitis virus (VSV), measles virus, and adenovirus, which causes the common cold. Adenovirus is one of the viral vectors used in some COVID-19 vaccines being studied in clinical trials. Viral vector vaccines are used to protect against: COVID-19 Viral vector vaccines A viral vector vaccine is a vaccine that uses an attenuated or harmless virus such as an adenovirus to deliver genetic material (DNA) that can be transcribed by the recipient's host cells as mRNA coding for a desired protein, or antigen, to elicit an immune response. Vectored vaccines are capable of inducing potent cell-mediated immunity, which is essential for complex disease like AIDS, malaria, and covid 19.  Passive immunization Passive immunization involves giving antibodies to an organism or to a toxin produced by an organism. Passive immunization is provided in the following circumstances: When people cannot synthesize antibody. When people have been exposed to a disease that they are not immune to or that is likely to cause complications. When people have a disease and the effects of the toxin must be ameliorated. Passive immunization does not induce natural immunity. Human immune globulin (IG) IG is a concentrated antibody-containing solution prepared from plasma obtained from normal donors. It consists primarily of IgG, although trace amounts of IgA, IgM, and other serum proteins may be present. IG very rarely contains transmissible viruses (eg, hepatitis B or C, HIV) and is stable for many months if stored at 4° C. The half-life of IG in the circulation is about 3 weeks. IG may be used for prophylaxis in people exposed to or at risk of Hepatitis A Measles Immunoglobulin deficiency Varicella (in immunocompromised patients when varicella-zoster IG is unavailable) Rubella exposure during the first trimester of pregnancy Disadvantages IG provides only temporary protection; the antibody content against specific agents varies by as much as 10-fold among preparations. Administration is painful, and anaphylaxis can occur.  IG types Intravenous immune globulin (IVIG) Intramuscular immune globulin (IMIG) Subcutaneous immune globulin (SCIG) Hyperimmune globulin While passive immunity is short-lived, it works right away, and hence it is preferred over active immunity in children or immunocompromised adults who are at high risk. For example, if a child suffers wild animal bites, passive rabies immunization is commonly administered. For people traveling to any country affected by hepatitis, doctors recommend passive vaccination to prevent it. This immunization is usually given on the day of their journey to cover their travel time. Passive antibody treatment is also done to prevent disease after a high-risk person is exposed to pathogens like tetanus, measles, syncytial virus, rabies, chickenpox, hepatitis A, , hepatitis B and covid 19 virus. Advantages of Passive Immunization 1.Passive immunization acts quicker, producing an immune response within hours or days of the administration, unlike vaccines, which take weeks or months to produce protective immunity. 2.Passive immunization also can override a deficient immune system, which is very helpful to persons who do not respond to vaccine immunizations. Disadvantages of Passive Immunization 1.Antibodies are costly to produce, however, new technologies can help produce them in the laboratory especially antibodies to infectious diseases that must be harvested from the blood of thousands of donors or even obtained from the blood of immune animals like those produced to neutralize snake venoms. 2.Antibodies from animals can cause serious allergic reactions in the recipient. 3.Antibodies must be administered via intravenous injection, which can be a complicated procedure and more time-consuming that the injection of a vaccine. 4.The immunity conferred by passive immunization is short-lived i.e it does not lead to the formation of long-lasting memory immune cells.