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A vaccine is an immunogenic agent that develops immunity against a disease. It can be administered by needle injection, oral administration, or aerosol. Vaccines are produced by degrading viruses or bacteria to the point that they can't spread (or replicate) themselves very easily, if at all.The principle of immunisation or vaccination is based on the property of ‘memory’ of the immune system. The antibodies produced in the body against these degraded viruses would neutralise the pathogenic agents during actual infection. There are 4 main types of vaccines : live attenuated vaccines, inactivated vaccines, toxoids, Subunit and Conjugate Vaccines. Examples of vaccines include polio vaccine, coronavirus vaccines such as covaxin, covishield, sputnik V vaccine, etc.
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Keyterms: Vaccine, Immunity, Immune system, Live attenuated vaccines, inactivated vaccines, toxoids, Subunit and Conjugate Vaccines, polio vaccine, coronavirus vaccines, covaxin, covishield, sputnik V vaccine
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Vaccination and Immunisation
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The terms vaccination and immunization are often used interchangeably. They seem similar but are different.
- Immunization is the process by which a person or animal stays protected from a disease. It may or may not happen due to vaccination. Eg. If a person gets chicken pox, chances of him getting it again is very low. In such a case, we say that his body is immune to chickenpox.
- On the other hand, vaccination is the process of administering a vaccine to a person to boost his immune system against a particular disease. A vaccinated person will be immune to a particular disease but an immune person may not have necessarily been vaccinated.
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Importance of Vaccination
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Vaccines are of major importance for young children and older people, as their immune systems tend to be weak. Vaccines save millions of lives every year by shielding against infections of a certain disease. The recent example of the novel coronavirus disease shows how a vaccine helps in controlling spread of harmful diseases.
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Types of Vaccines
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There are several types of vaccines:
- Live, Attenuated Vaccines:
These types of vaccines are developed in the laboratory by modifying a disease-producing virus or bacteria. When the developed vaccine is administered to a human, it will be unable to reproduce enough to induce disease, but it will also evoke an immune response that will protect against potential infection.
Some examples are Measles, mumps, rubella (MMR combined vaccine); Varicella (chickenpox); Influenza (nasal spray); Rotavirus.
- Killed or Inactivated Vaccines
A killed or inactivated vaccine is an alternative to live or attenuated vaccines. This kind of vaccine is made by inactivating a pathogen. The pathogen's ability to reproduce is destroyed, but it remains alive so that the immune system can detect it. Since killed or inactivated pathogens cannot replicate, they have less protection than live vaccines and are more likely to need boosters to establish long-term immunity.
Some examples are Polio (IPV); Hepatitis A.
- Toxoids:
Some bacterial infections are spread by a toxin released by the type of bacteria rather than the pathogen itself. Toxoids are vaccines made from inactivated toxins. Toxoids are usually classified as killed or inactivated vaccines, but they are often assigned their own category to emphasize that they contain an inactivated toxin rather than an inactivated type of bacteria.
Some examples are Diphtheria, tetanus (part of DTaP combined immunization).
- Subunit and Conjugate Vaccines:
Subunit vaccines use only a portion of a pathogen to elicit an immune response. This can be obtained by isolating a particular protein from a pathogen and introducing it as a stand-alone antigen.
Conjugate vaccines are similar to recombinant vaccines except that they are created by combining two distinct materials. Conjugate vaccines, on the other hand, are made from bacteria coat fragments. These coats are chemically bound to a carrier protein, and the resultant mixture is used to produce a vaccine. Conjugate vaccines are used to evoke a better, more detailed immune response. The bacterial fragment cannot induce disease, but when paired with a carrier protein, it will produce immunity to possible infection.
Some examples are Hepatitis B; Influenza (injection); Haemophilus influenzae type b (Hib).
Conclusion
Vaccines save millions of lives every year. When a particular section of a city or town is immunized against a communicable disease, several members of the same community are shielded against the diseases as the opportunity for an outbreak is minimized. Vaccines are based on the property of ‘memory’ of the immune system. Recombinant DNA technology has allowed the production of antigenic polypeptides of pathogens in bacteria or yeast. Vaccines produced using this approach have allowed large scale production and hence greater availability of vaccines.
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Sample Questions
Ques. What is it that prevents a child from suffering from a disease he/she is vaccinated against? Give one reason. [Delhi 2010] [1 mark]
Ans. The child is protected from the disease because vaccination produces antibodies, which help the child in fighting pathogens released during infection.
Ques. A boy of ten years had chickenpox. He is not expected to have the same disease for the rest of life. Mention how it is possible? [All India 2009][1 mark]
Ans. Upon contracting chicken pox once, the child’s immune system developed antibodies against the disease in large numbers. Further memory B-cells and T-cells are retained in the system, which trigger a more intense and quick response against the same antigen, thus preventing the occurrence of same disease in his life
Ques. How does a vaccine for a particular disease immunise the human body against that disease? [Delhi 2013c][2 marks]
Ans. During vaccination for a particular disease, an antigen or antigenic protein or pathogen which is in inactive form is introduced into the body which induces mild immune response.
The vaccine generates antibodies that neutralise the toxin/pathogen and produces memory B or T-cells, which recognise the pathogen in the subsequent encounters and produce antibodies.
Ques. Why does a doctor administer tetanus antitoxin and not a tetanus vaccine to a child injured in a roadside accident with a bleeding wound?[HOTS; All India 2010][2 marks]
Ans. Since the child is injured, he requires quick response from his body in order to fight the disease. The tetanus vaccine will take time to generate a proper response, which might become fatal for the child. A better and faster method to treat him will be tetanus antitoxin injection, i.e. preformed antibodies for tetanus .
Ques. (i) How does a vaccine affect immunity?
(ii) How can we get immunisation against tetanus?[All India 2010] [2 marks]
Ans. (i) The principle of immunisation or vaccination is based on the property of ‘memory’ of the immune system. Vaccines are produced by degrading viruses or bacteria to the point that they can't spread (or replicate) themselves very easily, if at all. The antibodies produced in the body against these degraded viruses would neutralise the pathogenic agents during actual infection.
(ii) Tetanus immunisation is done by injecting tetanus antitoxin injection, i.e. preformed antibodies for tetanus . This is known as passive immunization.
Ques. Explain the response initiated when a dose of vaccine is introduced into the human body. [Delhi 2009] [2 marks]
Ans. The principle of immunisation or vaccination is based on the property of ‘memory’ of the immune system. Vaccines are produced by degrading viruses or bacteria to the point that they can't spread (or replicate) themselves very easily, if at all. The antibodies produced in the body against these degraded viruses would neutralise the pathogenic agents during actual infection. Further memory B-cells and T-cells are retained in the system, which trigger a more intense and quick response against the same antigen
Ques. (i) Name and explain going reason, the type of immunity provided to the newborn by the colostrum and vaccinations
(ii)Name the type of antibody:
present in colostrum
produced in response to allergens in human body.[Foreign 2014] [3 marks]
Ans. (i) The immunity provided to the newborn by colostrum and vaccinations is called passive immunity. This is because both in colostrum and vaccines the antibodies conferred are not produced by own body but are rather transferred passively to recipient’s body. Such as IgA antibodies pass across the placenta or through milk (colostrum) to infants and provides passive immunity against infection.
(ii) The type of antibody present in
- colostrum is IgA.
- response to allergens in human body is IgE
Ques. (i) List any two situations, when a medical doctor would recommend injection of preformed antibodies into the body of a patient. Name this kind of immunisation and mention its advantages.
(ii) Name the kind of immunity attained when instead of antibodies, weakened antigens are introduced into the body. [Delhi 2008 C] [3 marks]
Ans. (i) Pre formed antibodies are injected in a patient when the response to the disease needs to be immediate and any delay can prove to be fatal, such as in case of snake bites and injuries. Such kind of immunity is known as passive immunity. Advantages of such injections are:
(a) Provides immediate relief.
(b) Used either prophylactically or therapeutically.
(ii)The process of administering weakened antigens into the body is known as vaccination. It produces active immunity in the body.
Ques. Is there any risk of getting vaccinated?[2 marks]
Ans. Vaccines, like any other drug, can cause side effects such as a low-grade fever or discomfort and swell at the injection site. Mild effects go out on their own after a few days. Serious, long-term side effects are exceedingly unlikely. Production of vaccines is licensed by the FDA in the US only after extensive tests to confirm that it is safe.
Ques. What are antigens?[1 mark]
Ans. Antigens are foreign substances that stimulate our immune system to produce antibodies.
Ques. What are the different types of antibodies?[1 mark]
Ans. Types of antibodies are IgA, IgE, IgG, IgM, and IgD.
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