Flu vaccines are prophylactic (disease-preventing) biologicals inoculated into susceptible individuals to protect against pathogens that could infect a host. Vaccines are an effective part of the practice of preventive medicine.
Flu Vaccine Use Early History and Rationale for Egg Embryo Cultivation
Flu vaccines were first prepared from viruses grown in embryonated eggs. Embryonated eggs are still used today because they are inexpensive, simple, reliable and have minimal side effects or dangers for immunization, except for those with egg allergies. Flu vaccines prepared from tissue cultures are available and are becoming the more common means for vaccine preparation.
Early vaccines contained only a single strain of flu. In recent years, the typical flu vaccine contains three different, potentially-infective strains. The viruses are inactivated, and are essentially dead. Vaccines are delivered intradermally via needle or air gun.
Flu Vaccine Injectable Types Contains Dead Virus
Flu vaccines that are injected contain only inactivated, dead virus. The virus is unable to reproduce and that is the measure of its being dead. Therefore, it is not possible to get the flu from these vaccines. Those who say they acquired the flu after injectable vaccination likely were infected naturally with a virus, whether cold or flu, from others with whom they visited, lived, or worked.
Flu Vaccine Manufacture, Strain Selection
The typical flu vaccine contains three current, or expected, epidemic or pandemic flu strains. Each strain is rapidly produced or cultivated in embryonated eggs. Viruses are harvested and used to inoculate more eggs. The viruses are checked for purity and strain characteristics. Viruses are harvested and separated out from most of the egg material. Viruses are killed and combined. Vaccines are tested for sterility and effectiveness. They are then ready for injection into vacinees.
Flu Vaccine How it Works, What the Vaccine Does, and Host Immune Responses
- Vaccine is intramuscularly (IM) injected to start the immunization process.
- Dead viruses in the vaccine are recognized by scavenger white blood cells termed macrophages.
- Macrophages phagocytose (eat, ingest) and process the viruses to small molecules.
- Processed, small, digested, viral molecules or molecular groups are displayed on the macrophage's surface membrane.
- T-helper cells (CD4 lymphocytes) contact and recognize the macrophage-presented antigen as foreign and recruit other white cells such as B-lymphocytes that make antibody, and killer lymphocytes that destroy virally-infected cells.
- B-cells begin to produce antibody, multiply their numbers and produce more antibody.
- After all the viruses are removed by cell and molecular responses, memory cells remain and retain memory of the antigenic encounters.
- B-cell clones are very specific. Each clone recognizes only one specific feature (epitope) of the virus, e.g. H1, or N1, or H5. H represents hemagglutinins and N represents neuraminidase.
- If H1N1 or H5N1 virus, or any other virus antigens in the vaccine are encountered weeks, months or years later during a natural infection, then the host's immune B and T cells will recognize and react with those antigens as they are recalled. The macrophages process the antigen, as they did with the vaccine. Antibody is produced rapidly by B cells and killer cells are activated. This is the immune system's anamnestic response. The invading virus is quickly inactivated and destroyed by this immune response. That's how the immune system works.The survival of mammalian hosts is intimately connected to their immune systems. Vaccines train the immune system to prepare for particular expected, or likely, microbial battles. The value of vaccination as a tool for survival and success in a microbial world cannot be underestimated—it is absolutely significant, important and essential! Read more about pandemics and epidemics and the influenza virus.
Sources
Brooks, G.F., J.S. Butel and S. A. Moore. 2004. Medical Microbiology. 23rd ed., Lange Medical Books, McGraw-Hill, New York. 818ppCDC (US). 2009.
Human Swine Influenza Investigation.
Donald Reinhardt - Think, read, write & live well always. DJR has a PhD in Biology/Microbiology & is a Fellow & Diplomate, ASM Amer Acad Micro.
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