VACCINE: DEFINITION, TYPES HOW IT WORKS ‘cine, suspension of weakened, killed, or fragmented microorganisms or toxins or other vacei biological preparation, such as those consisting of antibodies, lymphocytes, or messenger RNA (mRNA), that is administered primarily to prevent disease. A vaccine can confer active immunity against a specific harmful agent by stimulating the immune system to attack the agent. Once stimulated by a vaccine, the antibody-producing cells, called B cells (or B lymphocytes), remain sensitized and ready to respond to the agent should it ever gain enty to the body. A vaccine may also confer passive immunity by providing antibodies or lymphocytes already made by an animal or ‘human donor. Vaccines are usually administered by injection (parenteral administration), but some are given orally or even nasally (in the case of fiu vaccine). Vaccines applied to njusosal surfaces, such as those lining the gut or nasal passages, seem to stimulate a greater antibady response and may be the most effective route of administration. THE FIRST VACCINES Edward Jenner: smallpox vaccination The first vaccine was introduced by British physician Edward Jenner, who in 1796 used the cowpox virus (vaccinia) to confer protection against smalipox, to that use, however, a related virus, in humans. Prior the principle of vaccination was applied by Asian physicians who gave children dried crusts from the lesions of people suffering from smallpox to protect against the disease. While some developed immunity, others developed the disease, Jenner’s contribution ‘Was to use a substance similar to, but safer i i than, smallpox {¢ confer immunity, He thus exploited ne vi another viral disease. In 1881 French microbiologist Louis the relatively rare situation in which immunity to of» virus confers protection agai gainst Pasteur demonstrated immunizationHistorical Mase Vaccination Programs In The United Sixes ‘After Pasteur’s time, a widespread and intensive search for new vaccines was conducted, and vaccines against both bacteria and viruses were produced, aswell as_—_vaccines against venoms and other toxins. Through vaccination, smallpox was eradicated worldwide by 1980, and polio cases declined by 99 percent, Other wxamptes of diseases for which vaccines have been developed include mumps, measles, typhoid fever, cholera, plague, tuberculosis, tular emia, pneumococcal infection, tetanus, influenza, yellow fever, hepatitis A, hepatitis B, some types of encephalitis, and typhus—although some of those vaccines are less than 100 percent effective or are used only in populations at high risk. Vaccines against viruses provide especially important immune protection, since, unlike bacterial infections, viral infections do not respond to antibiotics, UNDERSTANDING HOW VACCINES WORK ‘The Immune System—The Body's Defense Against fufe:ton ‘To understand how vaccines work, it helps to first look «t how the body fights illness. When germs, such as bacteria or viruses, invade the body, they attack and multiply. This invasion, called an infection, is what causes disease. The immune system uses your white blood cells to fight infection. These white blood cells consist prunarily of macrophages, B-lymphocytes and T- lymphocytes: + Macrophagesmedia icou are white blood cells that swallow up and digest germs, plus dead or dying cells. The macrophages leave behind pans of the invading germns called antigens. The body identifies antigens as dangerous and stimulates antibodies to attack them, B-lymphocytes are defensive white blood cells; they can produce antibodies 10 fight off infection + Tymphocytes are another type of defensive white Ibod cell, that recognizes a familiar germ, if the body is exposed again to the same disease! The first time the body is infected with a certuin germ, ita take several days for the immune system to make and use all the tools needed to fight the infection, After the infection, the immune system remembers what it learned about how w protect the body against that disease. I your body encounters the same germ again, the T-Lymphocyies recognize the familiar germ and the B-lymphocytes oan produce antibusiae ts fight ott Ao festion,HOW VACCINES WORK Vaccines can help protect against certain diseases by imitating an infection. This type of imitation infection, helps teach the immune system how to fight off a future infection Sometimes, after getting a vaccine, the imitation infection can cause minor symptoms, such as immunity. fever. Such minor symptoms are normal and should be expevied as the body build | Once the vaccinated body is left with a supply of T-lymphocytes and B-lymphocytes that will remember how to fight that disease. However, it typically takes a few weeks for the body to produce T-lymphocytes and B-lymphocytes after vaccination. Therefore, it is possible that a person infected with a disease just before or just after vaccination could develop symptoms and get that disease, because the vaccine has not had enough time to provide protection. While vaccines are the safest way to protect a person from a disease, no vaccine is perfect. It is possible to get a disease even when vaccinated, but the person is less likely to become seriously ill. VACCINE ‘Vaccines are medications that are used to make people immune to certain diseases. They contain the bacteria or virus, or parts of the bacteria or virus, that cause illness and disease. The bacteria or virus is included in the vaccine so that i immune system can be taught to recognize and produce antibodies against it if a person is exposed to it naturally, without the person ever experiencing any symptoms of illness or disease. ‘The main types of vaccines that act in different ways are: Live-attenuated vaccines Inactivated vaccines + Subunit, recombinant, conjugate, and polysaccharide vaccines + Toxoid vaccines + mRNA vaccines + Viral vector vaccines ‘There Is a risk of side effects with all vaccines, but some are less likely to cause side effects than others.Live-attenuated vaccines Livecattenuated vaccines inject a live version of the germ or virus that causes a disease into the ttemt .ecines inject a Ii the germ or t causes a di it body. Although the germ is a live speci eaken . sian as tt 1s unable to reproduce once it is in the body. men, it is a weakened version that daes net eause any symptoms of infee Live-attenuated vaccines can be made to create immunity against viruses or bacteria, but they are more commonly used for viruses. This type of vaccine works by allowing a virus or germ to reproduce enough for the body to make memory B-cells, which are a type of cell that can recognize and remember a virus and generate an immune response against it for many years after their initial response. Live-attenuated vaccines trigger an immune response that is similar to what would occur during natural infection, but the person is not able to pass on the virus to other people and will not ‘become ill with the disease the virus causes, A person will usually get lifelong immunity from disease through live-attenuated vaccines. and only one or two doses of the vaccine are usually needed to provide this immunity, The types of diseases that live-attenuated vaccines are used for include: 1 + Measles, mumps, and rubella (MMR combined vaccine) © Rotavirus + Smallpox + Chickenpox + Yellow fever Live-attenuated vaccines also need to be kept cool while they are stored, so they may not be Suitable for use in environments where there is litle access to teftigeratior n,Inactivated vaccines it i i ‘ith heat or ‘An inactivated vaccine uses a strain of a bacteria or virus that has been killed wi chemicals, This dead version of the virus or bacteria is then injected into the body. Inactivated vaccines are the earliest type of vaccine to be produced, and they do not trigger an immune response that is as strong as that triggered by live-altenuated vaccines. Inactivated vacelnes co not offer lifelong immunity an need topping up over time, but they may cause fewer side effects than live-attenuated vaccines. - | The types of diseases that inactivated vaccines are used for include: + Hepatitis A + Flu + Polio + Rabies Subunit, recombinant, conjugate, and polyancehuride vaccines Subunit recombinant, conjugate, and polysaccharide vaccines use particular parts of the germ or Vins. They can tigger very strong immune responses in the body because they use a specific part of the germ. conditions. ‘These types of vaccines are used to create immunity against the following disease: S: Hib Hemo, Hepatitis B ‘Human papillomavirus (HPV) Whooping cough Pneumococcal disease Meningococcal disease Shingles philus influenza type b)Subunit vaccines Antigens from the surface of the germ or virus are responsible for triggering an immune response in the body. Subunit vaccines isolate specific antigens from a germ or virus for nae in the ‘yaceine, and these antigens are specifically chosen according to the strength of the immune response they generate. Subunit vaccines do not cause many side effects because they are so specifically targeted. Recombinant vaccines Recombinant vaccines are made through genetic engineerin; The gene that creates the protein for a bacteria or virus is isolated and placed inside another cell’s genes. When that cell reproduces, it produces vaccine proteins that mean the immune system will recognize the protein and protect the body against it. Conjugate vaccines Conjugate vaccines use two different components. Conjugate vaccines use parts from the outer antigen coat of the bacteria or virus, which are not strong enough to cause illness or generate an ‘immune response in the body, These weak antigen coats are linked to a stronger cartier protein using chemicals, and this combination of the weak antigen coat and stronger carrier proteins triggers the immune system to act more aggressively against the weak antigen. Polysaccharide vaccines similarly to conjugate vaccines,‘Toxoid vaccines oxoid vaccines use toxins created by the bacterla or virus to create immunity to the specific parts of the bacteria or virus that cause disease, and not the entire bacteria or virus. The immune response is focused on this specific toxin, Toxoid vaccines do not offer lifelong immunity and need! to be topped up over time. ‘Toxoid vaccines are used to create irhmunity against diphther‘a and tetanus. mRNA vaccines j | This technology has been in development for decades. mRWA vaccines have benefits such as short manufacturing times and low manufacturing costs. (owever, they have to be kept at low temperatures due to the fragility of the mRNA. mRNA vaccines work by triggering an immune response from proteins they synthesize. They induce both cellular and humoral immunity. The first mRNA vaccine was approved this year for COVID-19. There is some misinformation that mRNA vaccines can alter a person’s DNA. However, they are not able to do this. Viral vector vaccines Viral vector vaccines modify another virus and use it as u ¥2etor to deliver protection from the intended virus. Some of the viruses used as vectors includé edenovirus, influenza, measles vis and vesicular stomatitis virus (VSV), : a Recent uses of viral vector technology have been i een in Ebola virus and ies i its use for Zika, flu and HIV are ongoing. ee tetpNA and recombinant vector vaceines ged yaceines) are two new DNA and recombinant vector vaccines (also known wv nln forme! types of vaccines currently under development. DNA vaceines include DNA that creates specific antigens from a germ. Onee injected into the body, the DNA for the germ is reproduced by the body and is recognized by the mm protect the body against futher infection and will conti june system. The immune response will then inue to protect the future ve than petein- or antigen-based vaccines because DNA vaccines are thought to be more effecti ‘ody before the immune system can the antigen can sometimes be degraded or consumed by the 1 generate a full attack against the antigen. on nnd are good at training the immune Recombinant vector vaccines work as a natural infec system to recognize and attack germs. They work by reproducing a live virus that has been engineered to carry extra genes from the germ infecting the body. The extra number of genes produce the proteins that the immune system needs to recognize and protect against, Types of Vaccines, Animation Summary There are four types of vaccines that are widely used agalrist several diseases, but there are ne Le . Wy types of vaccines being developed that may be cheaper rnd provide longer i i existing vaccines. mger immunity than \ Some existing types of vaccines will cause more sid eff : + efBrets attenuated vaccine, which may not be suitable for people fi s than others, such as the live- “ le Vivi it or people with a weakened immune eystem, ple living with long-term health conditionsile some vaccit ive versi . ™ ines use live versions of a particular virus or bacteria, other vaccines can use only a part of the virus or bacteria to trigger an immune response, which may produce stronger immune action against the germ because of its specificity. Medical advice should be sought before being vaccinatul ayamst a particular disease. REFERENCES * Antia, Ret al. Recombinant vector. =—vaccine evo) 2019). https:fjournals plos.org’ploscompbioVarticl:? d=10.1371%2Fjournal. pet: 31 CDC. (2012). httpsilAwww.cde.gov/vaccines/vpa. vp {-vae-basics. html + coc. (2018). https://www.ede.gov/vaccine vhep/conversations/understanding work html «History of Vaccines. (2018). https:/Avww-historyot types-vaccines saccines org/content/articles/ dit + The Immunisation Advisory Centre. (2020). bitps://www-immune.org.nz/vaccines/vweine-developmenttypes-vaceines ‘Vaccines. (2020). https://www.vaccines.gov/basies/iypes