What is Vaccines? Definition, Types, Benefits, Risk

What are Vaccines? How Vaccines are Produce, Definition, Types, Benefits, Risk: 


  • Vaccines are the biological preparation produced in the laboratory whose main function is to train the immune system against different types of infections, as they stimulate the production of antibodies.
  • Antibodies are the substances produced by the body to fight invading microorganisms. 
  • Thus, the body develops antibodies before it comes into contact with the microorganism, leaving it ready to act more quickly when that happens.
  • Vaccination is the most effective and safe way to prevent and protect our bodies against certain infectious diseases.
  • The vaccine is given in any form orally or by injecting it into your body.
  • Vaccination works by increasing the immunity of the person to destroy the microorganisms produced in the body.

Definition of Vaccines

  • A vaccine is a biological preparation that provides active acquired immunity to a particular infectious disease caused by bacteria and viruses.

  • The medicine which is given in drops, injections, or any other form to develop immunity against infectious disease is called vaccine and the process is called as vaccination. 

What is a vaccine?

  • When a virus or bacteria enters the body, they invade the cells, where they reproduce and multiply. This multiplication is called infection and this process will result in disease. 
  • Immediately, the organism tries to defend itself, initiating the production of antibodies. 
  • However, this process can take a few days, and there are not always guarantees that it will be effective.
  • Vaccines are biological substances that, when introduced into the body, stimulate the immune system to produce antibodies.
  • Therefore, when a person is vaccinated, they already have antibodies, which are ready to attack the virus or bacteria that enter their body. Thus causing an immediate immune response.
  • In this sense, immunization begins in childhood. Since the beginning of life, we have stimulated the human body's natural defenses, preparing the body to fight diseases safely and effectively. 
  • Thus, the vaccine avoids the risks of complications of the disease and prevents its proliferation in the family, school, and social environment, for example.
  • In addition, vaccination should also continue into adulthood, as some of these substances must be administered throughout life. 
  • So be sure to follow the immunization schedule and be up to date with your vaccines. After all, vaccines save lives!

History of vaccination

  • Vaccines emerged mainly due to the need to reduce the number of deaths caused by communicable diseases. 
  • The history of immunization is marked, initially, by the search for the control of smallpox, a disease known since the dawn of humanity, around 10 thousand years BC, and which decimated several populations.
  • British physician Edward Jenner (1749-1823), is considered the first carried out with scientific methods and to whom the discovery of the vaccine is credited.

How does a vaccine work?

  • In normal conditions, our immune system fights against any kind of disease and protects us from it. 
  • In some people, the immune system is strong or weak. 
  • When a pathogen enters our body and starts causing infection, our body recognizes this pathogen as a foreign particle and tries to kill them. 
  • In such a situation, our body automatically starts making a kind of protein which is called antibodies.
  • Sometimes our immune response is weaker than pathogens, to enhance our immunity vaccines are taken.
  • The vaccine may contain live or kill bacteria or viruses of diseases like hepatitis B, measles, tetanus, polio, and whooping cough, etc. 
  • They are injected into our body, and automatically start making antibodies to fight them and protect us, and once made, these antibodies are always present in our body and whenever in future this disease which we have vaccinated and saved. 

Types of vaccines:

Vaccines can be classified into two main types, depending on their composition:

  1. Live, Attenuated Vaccines
  2. Inactivated or killed vaccine
  3. Subunit Vaccines
  4. Conjugate Vaccines
  5. DNA Vaccines
  6. Recombinant Vector Vaccine

1. Live Attenuated Vaccines

  • In this type of vaccine, the infectious microorganism undergoes a series of procedures in the laboratory that decrease its pathogenicity. 
  • Thus, when the vaccine is administered to the human body an immune response is stimulated against this microorganism, but the disease does not develop, as the microorganism is weakened. 
  • The first vaccine for cowpox developed by Jenner is of this type.
  • Examples of these vaccines are the BCG, MMR, and chickenpox vaccines.
  • Generally, attenuation achieves by growing pathogens under abnormal culture conditions.
  • For example, Attenuated strains of Mycobacterium Bovis called BCG ( Bacillus Calmette-Guerin was grown on a medium containing high concentrations of bile.
  • The advantage of live attenuated vaccines is it gives a strong immune response and also provide lifelong immunity with few doses.
  • The disadvantage of live attenuated vaccine is it requires refrigerated storage and may mutate to a virulent form.

2. Inactivated or Killed vaccines

  • This type of vaccine contains microorganisms, or fragments of these microorganisms, that are not alive and stimulating the body's response, as is the case with the hepatitis vaccine and the meningococcal vaccine.
  • From the moment the vaccine is administered, the immune system acts directly on the microorganism, or its fragments, promoting the production of specific antibodies. 
  • If in the future the person comes into contact with an infectious agent, the immune system can already fight and prevent the development of the disease.
  • The inactivation of epitopes is done by heat inactivation or chemical inactivation.
  • Inactivated or Killed vaccines are prepared against diseases such as cholera, plague, influenza, hepatitis, Polio, Rabies, etc.
  • The advantages of this vaccine are stable, safer than live vaccines, and refrigerated storage is not required.
  • The disadvantage of this vaccine is it provides a weaker immune response than live vaccines and booster doses required.

Examples of Vaccines

  • BCG protects against severe forms of tuberculosis, meningeal and miliary.
  • Hepatitis B: used to combat hepatitis B.
  • DTP+Hib+HB (Penta):  immunizes against diphtheria, tetanus, whooping cough, Haemophilus influenzae B, and hepatitis B.
  • Poliomyelitis 1, 2, 3 (VIP):  composed of three doses, it is used in the fight against poliomyelitis.
  • Human Rotavirus G1P1 (HRV): protects against diarrhea caused by rotavirus.
  • Meningococcal C (Conjugate): immunizes against type C meningococcal meningitis
  • Yellow Fever (Attenuated):  Used to protect against yellow fever.
  • Polio 1 and 3 (POV):  protects against poliovirus types 1 and 3.
  • Diphtheria, Tetanus, and Pertussis (DTP):  protects against diphtheria, tetanus, and whooping cough.
  • Measles, Mumps, Rubella (MMR): immunize against measles, mumps, and rubella.
  • Measles, Mumps, Rubella, Chickenpox (SCRV):  protects against measles, mumps, rubella, and chickenpox.
  • Hepatitis A (HA): used to fight hepatitis A.
  • Chickenpox:  protects against chickenpox.
  • Diphtheria, Tetanus (DT):  Immunizes against diphtheria and tetanus.
  • Human Papillomavirus (HPV):  fights Human Papillomavirus 6, 11, 16, and 18 (recombinant).
  • Influenza protects against influenza.

Stages in the Vaccine manufacturing process: 

The development of any vaccine involves several steps, starting from research and research and extending to manufacturing, quality control, and distribution. The following are the steps in vaccine manufacturing-

1. Research: Scientists researching vaccine manufacturing identify natural and artificial antigens, which can help in the prevention of any disease. Once the antigen is recognized, it is synthesized to induce an immune response. This step involves the growth and collection of microbes or the production of a recombinant protein (a protein that is made by DNA technology) from that pathogen.

2. Pre-Clinical: In this, a cell culture system is used and it is tested on animals, this ensures the efficacy of the vaccine. In the course of testing, vaccines are used on rats, monkeys, rabbits, etc. In this phase, scientists want to test whether the vaccine produces resistance in an animal or plant. If resistance does not arise, then start again from the first stage, and if resistance develops then enter the third stage.

3. Clinical Trial: This stage is the most sensitive and important in the development of a vaccine because, in this, the resistance generated in animals or plants through the cell culture system is tested on the human body. This phase consists of three phases, which are as follows-

  • Phase 1: In this, the vaccine is used on a small group of people (about 20 to 80 people) and it is tested on how the vaccine is affecting the human body. In this period of supervision, special care is taken of the dosage and timing of the vaccine.

  • Phase 2: The group of people to whom the vaccine is to be given, is increased to the number of hundreds of people. In this, changes are made in the dosage of the vaccine, and the ability of the vaccine to produce favorable and adverse effects is also analyzed. Efforts are made to involve people of all age groups in this stage. It takes an average of 8 to 12 months.

  • Phase 3: In this stage, the vaccine is tested on a group of several thousand people and an attempt is made to assess how the vaccine produces an effect in a large population. At this stage, the long-term effects of the vaccine are studied. When it is established that all the objectives of the test have been achieved, it is taken forward for regulatory review.

4. Regulatory review and approval: At this stage, all phases of vaccine trials are reviewed by the Drug Controller General of India (DCGI) based on the standards set by the World Health Organization. After that, the manufacturing of that vaccine is approved.

5. Manufacturing and quality control: At this stage, the work of manufacturing the vaccine with better infrastructure is started. To maintain the quality of the vaccine, quality testing is done from time to time by scientists and regulatory authorities.

Benefits of vaccines:  

There are multiple benefits provided by vaccines, the Ministry of Health, Social Services, and Equality on the occasion of the European Vaccination Week have drawn up a decalogue with the benefits.

  • Vaccines save lives every year. 
  • Vaccines help to fight against diseases, making it possible to control, eliminate and even eradicate them.
  • Vaccination is important throughout life, it does not end in childhood
  • Prevents complications of infectious diseases and some types of cancer.
  • It provides social and economic benefits.

Frequently asked questions about vaccines

1. How are vaccines made?

Answer: They are substances produced in laboratories to stimulate the immune system to produce antibodies even without having contact with the offending microorganism. These substances may contain live attenuated, dead, or just fragments of microorganisms.

2. Does vaccine protection is life longer Immunity?

Answer: Yes, But in some cases, the immunological memory lasts a lifetime however in others it is necessary to have a booster of the vaccine, as is the case of diphtheria or tetanus.

3. Can vaccines be used in pregnancy?

Answer: Yes. As they are a risk group, pregnant women should take some vaccines, such as the flu, hepatitis B, diphtheria, tetanus, and whooping cough vaccine, which are used to protect the pregnant woman and the baby. Administration of other vaccines should be evaluated on a case-by-case basis and prescribed by the physician.

4. Can more than one vaccine be taken at the same time?

Answer: Yes, The administration of more than one vaccine at the same time does not harm health.

5. What are combined vaccines?

Answer: Combined vaccines are those that protect the person from more than one disease and in which only one injection is required, as is the case with the triple viral, retroviral or bacterial Penta, for example.

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