All About Vaccines


all about vaccines

Vaccines: Introduction


Vaccines have been used throughout history.

This paper will be giving an insight into the development of vaccination, aspects that are taken into consideration while developing a vaccine, how they stimulate Immune response in the body of a vaccinated individual, and the need for a vaccine for community-level protection. 


Background

A vaccine has been described by experts as a biological substance designed to protect humans from infection caused by bacteria or viruses.

It is said to encourage one’s immune system to develop similar antibodies as to what would have been produced if one was infected with the disease.

Through vaccination, an individual develops immunity to the disease without being infected by it.

A vaccine is used to prevent diseases, unlike other medicines that treat or cure the infection.        

Edward Jenner is known to be the founder of vaccinology in the Western part of the world after developing a vaccine for smallpox in a scientific manner, it has been said that in other parts of the world individuals used a similar concept to prevent infection.

Jenner was the first to be able to give it a scientific status and conduct a scientific investigation. 

His hypothesis was that infection with cowpox protects against chances of later development of smallpox infection.

It has been recorded that on May 14, 1976, Edward Jenner scratched fresh cowpox lesions which he had found in a young dairymaid’s hands and arms into an eight-year-old boy named James Phipps.

Thereafter, it was noted that Phipps developed mild fever and discomfort in the region under the shoulder joint.

In later days he lost his appetite and left cold, but on the tenth day of observation, he was noted to have felt much better.

Jenner later in July of 1796 inoculated matter from a fresh smallpox lesion in Phipps, no disease development was observed in the boy, which led Jenner to conclude that protection was complete. 

The Latin word for cow is Vacca, and vaccinia stands for cowpox; which inspired Jenner to name this method of preventing the disease as vaccination. 


1. Development concept of vaccine 

When a vaccine is being developed the process is said to go through preclinical and clinical studies to determine the safety and efficacy of the development substance.

The development of the vaccine process before going through evaluation is said to involve taking a new antigen or immunogen identified in the research process and developing the given substance into a final vaccine. 

Better knowledge about the immune system and host-pathogen interaction has been said to help stabilize the rational design of vaccines.

It has been said that vaccines that include, protein subunits, pathogens, particles similar to the pathogen, polysaccharides, use of viral or bacterial vectors, in addition to adjuvants and conjugation technology are used in the design toolbox for better, broader, and increased immune response.

To develop a substance, a sufficient amount of research is required to gather information/knowledge in regards to-

1. Pathogen life-cycle & epidemiology: Knowledge of pathogen structure is said to be taken, interaction with cellular receptors is noted, route of entry, successive replication sites, and disease-causing mechanisms are all consider to be important to identify antigens appropriate for the prevention of disease and infection.

The demographics of disease is noted, precise risk group and infection which are specific to age rates are said to be used to determine the correct age and the specific population that is to be immunized

2. Immune control & escape: Exploration of the interaction between host and pathogen is said to be done, with the motive to establish comparative importance of antibodies, T-cells of different types and innate immunity, strategies for immune escape during infection, and feasible immune correlates of protection.

This information gives a map to identify and select antigens and the particular immune response that is essential for protection.              

3. Antigen selection & vaccine formulation: The selected antigen is developed to stability give appropriate immunogenic over time, persuade an immune response which most likely to be protective, plus be governable to later increase and have high commercial production.

4. There needs to be preclinical & clinical testing of the vaccine. The developed vaccine needs to be examined for immunogenicity, safety, and efficacy is tested in preclinical and well-structured clinical trials.

General rule: The more similar a vaccine is to the disease-causing form of the organism, the better the immune response to the vaccine. 


2. Classification of vaccination

The basic two types of vaccines are said to be live attenuated vaccines and inactivated vaccines, other types are polysaccharide and recombinant. 


2.1 Live Attenuated Vaccines

Live attenuated vaccines are said to be produced from live “wild” viruses and bacterias which are weakened in laboratories through culture, which can be a chemical or physical process.

For the immune response, they must replicate in the body of the injected.

It is said that the immune system does not differentiate between an infection caused by a wild virus and infection caused by a weakened vaccine virus, because of which the immune response to a live, attenuated vaccine is said to be identical to a natural infection caused by wild virus.

These vaccines are said to produce immunity in most receivers in one dose, though a small percentage of receivers are said to not respond in the same manner, hence a second dose is recommended for a high level of immunity in the population.

Live attenuated vaccine which is taken orally is said to require more than one dose to produce immunity. 


2.2 Inactivated Vaccines

Inactivated vaccines are said to be produced by killing organisms physically or chemically. The organism can be a whole cell or fractional.

As the organisms in these vaccines are not alive they cannot replicate. It is said that these vaccines can not cause diseases in receivers with immunodeficiency.

These vaccines’ immune response is said to be mostly antibody production, it has been told that inactivated vaccines require multiple doses to produce immunity.

It has been stated that in general inactivated vaccines do not produce immunity in the first dose but prime the immune system and a protective immune response is said to develop after the second or third dose of the inactivated vaccine.

Some inactivated vaccines are said to require periodic supplements to increase antibody titers. 


2.3 Polysaccharide Vaccines

Polysaccharides vaccine is described to be a unique type of inactivated vaccine which consists chains of sugar molecules that make up the surface capsule of a certain bacteria.

The typical immune response of this vaccine is said to be  T-cell-independent resulting in stimulation of B-cells without the help of T-helper cells.

These vaccines are hypothesized to not be consistently immunogenic in children below 2 years it is assumed to be because of the immature immune system


2.4 Recombinant Vaccines

Recombinant vaccines are produced by genetic engineering of antigens.
Insertion of a segment of the respective viral gene into the gene of a yeast cell or virus is said to be done to produce the vaccine.

Pure Hepatitis B surface antigen,HPV capsid protein, or influenza hemagglutinin is said to be grown by the modified yeast cell or virus.

The generation of Serogroup B meningococcal vaccines are proteins and outer membrane vesicles, is said to be done recombinant technology, it is also been states that not all vaccines generated by this technology have only a part of the organism, few consistent a whole of it.


Table1- development of the human vaccine 

Live Attenuated VaccineInactivated Vaccines Polysaccharide Vaccine ReassortantVaccine Recombinant Vaccines
Eighteenth centurySmall pox 
Nineteenth century Rabies TyphoidCholera Plague   
Early twentieth century BBG (Tuberculosis)Yellow Fever Pertussis (Whole Cell)InfluenzaRickettsia DiphtheriaTetanus 
Late twentieth century Polio (OPU)MeaslesMumpsRubella (ca)Adenovirus Typhoid  Ty 12aVaricella Cholera CVD103 InfluenzaPolio (IPV)Rabies(New)Anthrax Japanese encephalitis Hepatitis ATrick- borne encephalitis E.coli (+CTB)    Pneumococcus MeningococcusHepatitis B (plasma-derived)H. Influenza meningococcus (protein conjugated)Influenza (killed+live) Hepatitis B recombinant Cholera toxinPertussis toxin
Twenty-first century ZosterPneumococcal conjugate Rotavirus Human papillomavirus 


3. Benefits Of Vaccination. 

Vaccines have been reported to provide not only individual levels of protection for those who are vaccinated but also provide community protection by reducing the spread of the disease within a population.

It has been stated that infection from an individual to another spreads when the transmitting case comes in contact with a susceptible person, however, if the transmitting cases come in contact with immune individuals, the infection is said to not spread beyond the index cases and is controlled within the population.

It is claimed that even if 100% immunity is not present the chain of the infection spreading from an individual to another can be interpreted due to transmitting cases not being able to have contact with a large number of susceptible individuals, this phenomenon has been referred to as “herd immunity” or “community protection” and is said to be an important benefit of vaccination. 

The principle of vaccination is to induce protection against a pathogen by mimicking its natural interaction with the human immune system. The vaccine reduces the risk of complications and mortality following subsequent exposure to an infectious agent.


3.1 Individual protection

The vaccine is said to protect individuals by protecting them from infections.

Vaccination of infants with several antigens is said to be considered the main source of success in immunization programmer against the cluster of childhood diseases.

Few vaccines are said to protect an individual from infection even after being taken post-exposure to an infection, rabies, hepatitis B, hepatitis A, measles, and varicella are examples of such vaccines. 


3.2 Herd Immunity

 Herd immunity has been stated to occur when a large number of a population is immune to disease either through vaccination or prior illness, which is said to make the spread of the infection from an individual to another less likely, the individuals who are not vaccinated too are provided with some protection because of the interruption in the chain of spread within the community giving the disease fewer chances of infecting a large percentage of a population.


3.3 Source Drying 

Source drying is said to be related to the concept of heard protection.

A population is protected by target vaccine when a percentage of the population is identified to be carriers of the infection, this helps in controlling and decreasing the disease.

Those who are too young to be vaccinated are to be protected by this method. 


3.4 Increasing Life expectancy 

Vaccines have been said to increase life expectancy by providing protection from harmful diseases. 

It has been noted that the senior citizens of the United States of America who were given influenza shots

were 20% less likely to suffer from cardiovascular and cerebrovascular disease. They have been said to have 50% less risk of mortality when in comparison to unvaccinated senior citizens of the same country. 

In hospital risk of mortality among senior citizens of Sweden has been noted to have reduced by administration of polysaccharide pneumococcal vaccine and inactivated influenza vaccine for pneumonia and cardiac failure among senior patients, a better response has been noted when a patient is given both the vaccine. 


3.4 Help for the economy 

Vaccination helps in preventing infection before an individual is infected.

Keeping the population healthy acts as a workforce for a nation which leads to increased productivity and gain. Vaccination has been considered to be the bedrock for public health programs in third-world countries. 


3.5 Provides safe travel and mobility 

Influenza and hepatitis A are noted to be the most common vaccine-preventable disease among travelers.

Rabies, hepatitis B, typhoid, yellow fever, Japanese encephalitis, and measles are also advised to be considered for travel vaccines.

To ensure early protection, a number of vaccination can be given by flexible speeded-up schedules helping travelers looking for health advice with the limited time period before departure, they can travel overseas without having to worry about vaccine-preventable health risks to themselves and others.


Conclusion

Over the past years, vaccination has been developed with new technological ways to provide immunity to prevent diseases.

A number of aspects are taken into consideration to ensure the safety of the vaccine, but still no vaccine is graded as 100% safe and effective for everyone.

Different kind of vaccines gives a different kind of immune response in a vaccinees body to prevent future chances of infection.

Vaccine not only protects individuals but is deemed to be beneficiary at a community level.

It is said to help in breaking down the chain of spread within a population hence has helped in decreasing the risk of mortality.

It has been noted to increase the life expectancy rate by protecting the venerable population.

The benefits of vaccination are seen not only in Health Sector but have been noted to give socioeconomic benefits too. Infections disease become less common and can be controlled with vaccines. 

(Note- readers are requested not to take the content given above as a substitute for a professional’s advice. They are highly encouraged to consult a medical professional before taking a vaccine)     





References

[1] https://www.cdc.gov/vaccines/vpd/vpd-vac-basics.html
[2]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1200696/
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