Hello, guys. Welcome to another new article. In this, we will learn what a vaccine is. To learn about the vaccine completely step by step, let’s start.
Definition of the vaccine?
Vaccines are diluted suspensions of killed, living, or attenuated microorganisms or their component or metabolic products used as antigens to produce Immunity against infection caused by these microorganisms.
When injected in a normal, healthy person, vaccine-induced antibodies provide acquired Immunity against subsequent infection from that specific microorganism.
Role of vaccines
The injection of vaccine is called a ‘shot’. The shot involves the injection of an attenuated microorganism Whose violence is weakened in the ability to cause disease is lost, but it is capable of inducing body formation.
Vaccines have been effective in developing resistance to infection of microorganisms that cause Cholera, diphtheria, measles, Mumps, whooping cough, rabies, smallpox, tetanus, Typhoid, yellow fever, and poliomyelitis.
Because of the worldwide immunization campaign against smallpox, w h o in 1980, it declared that the smallpox virus was completely eradicated from the world.
How many types of vaccines?
Scientists have developed both bacterial and viral vaccines.
Bacterial vaccineÂ
These may be :
- live vaccines like BCG for tuberculosis
- Killed vaccines like TAB for enteric fever.
- Subunit vaccine like v1 polysaccharide for Typhoid.
- Bacterial products like toxoids for diphtheria and tetanus.
2. Viral vaccine – these are also of the following three types.
- Live vaccine – the oral polio vaccine is the Sabin vaccine.
- Killed vaccine – injectable polio vaccine or Salk vaccine.
- Subunit as a vaccine –Â hepatitis b vaccine.
1. Live vaccineÂ
The live vaccine contains live attenuated viruses. These viruses are Bacteria that act like natural infections, multiply in the host, stimulate Antibody production, and confer long-lasting Immunity. But these have weakened violence and are unable to cause the disease. The attenuated viruses are mutant strains of Virulent wild-type. These are obtained.
- By selecting naturally attenuated strains.
- Cultivating the virus Serially in various hosts and cultures to obtain attenuated strain.
- Planned Genetic alternation in the virus.
The live vaccine is against poliomyelitis, smallpox, mumps, measles, yellow fever, and rubella.
Advantage
The live vaccines have the following advantages:
- The live vaccines are more effective than the killed vaccines.
- A single dose is usually sufficient.
- The live vaccine induces a wide spectrum of immunoglobulins or antibodies to various antigens.
- Live vaccine-induced cell-mediated Immunity.
- The live vaccine provides long-lasting Immunity.
Disadvantage
The live vaccine has the following disadvantages.
- Live attenuated viruses have changes of reversion to Greater virulence during multiplication.
- There are changes in its contamination with potentially dangerous viruses like Oncogenic viruses (Avian leukosis virus, simian Papo virus SV 40, and simian cytomegalovirus).
- There is a potential problem with the spread of viruses from vaccines to contacts.Â
- Interference with the coinfection of pre-existing wild types of viruses may decrease the efficiency of the vaccine.
- Liver vaccines are heat labile, so these need to be stored under refrigeration. These have limited shelf life.
Killed vaccine
Killed vaccines are made by inactivating virus heat phenol Formalin or beta propiolactone. The viral protein coat is used as an antigen. Therefore, the killed virus vaccine stimulates circulating antibodies against coat protein. The killed vaccine is used against rabies, influenza, Japanese B encephalitis, and Hepatitis – B.
Killed vaccines are stable, non-heat labile, and quite safe. These can be used in combination with polyvalent vaccines, and they do not have the danger of spreading.
The killed vaccine is less immunogenic, and resistance or Immunity lasts only briefly. Therefore, repeated doses (maybe 2-3 or more) are needed for developing Immunity. The first was the primary dose, and the subsequent was called the booster dose.
Viral vaccines
Immunity to viral infection is based on developing antibodies in response to specific antigens located under the surface of viral particles. Vaccines are now available to prevent significant human diseases like influenza, smallpox, measles, mumps, hepatitis B encephalitis, yellow fever, and poliomyelitis. There is no medicine against viral infection. This means that Immunity against infection is the only solution to viral infection.
Salk and Sabin vaccines
Salk and Sabin vaccines are polio vaccines prepared by Salk and Sabin separately from the poliomyelitis virus. These vaccines are Salk’s killed polio and Sabin’s live polio vaccines.
Salk’s killed polio vaccine, or Salk vaccine, is a formalin-inactivated preparation of three types of poliovirus grown in monkey kidney tissue culture. It was prepared by Salk in 1953. It gives 80 – 90% protection against poliomyelitis. Salk’s vaccine is injected and named inactivated injectable polio vaccine (IPV). Its 3 doses are given 4–6 weeks apart. This primary vaccination is followed by a booster dose 6 months later. The first dose is recommended at the age of 6 months.
Sabin’s live vaccine was developed independently by Koprowski, Cox, and Sabin, attenuated by a repeated passage in cotton rats. The vaccine contained attenuated strains of all three types of polio. Live poliovirus is administered orally, and it is known as the oral polio vaccine (OPV).
It is now prepared by growing attenuated strains in monkeys’ kidney cells. Theoretically, one dose is sufficient to establish Immunity, but in practice, 3 Doses are given at 4 to 6 weeks intervals, and the first dose is given to the Infant when he is 3 to 4 months old.
In tropical countries, 5 instead of three doses are recommended. One or two doses of live vaccine produced 90-100% immunity in developed countries but not in underdeveloped ones.
Conclusion
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