Introduction
During the infection is occurred, the ability of host to make a sufficient immune response affects the ability of its fighting the infection. The immune system involves abundant organs, cells, molecules and pathways and all they are connected to each other. The immune system is spilted into two major types: the innate and adaptive immunity.
The difference between innate immunity and adaptive immunity; the innate immunity is a fast and non-specific responding when the first encounter of pathogens, while the adaptive immunity is highly specific responding that leading to develop memory cells, it is stronger and long-lasting. The concept of building protective immune is the ability to recognize and remember a pathogen by the immune system.
Immunization is significant tool to prepare the host when the re-encountering of the pathogen is occurred by build a protective immunity. Immunization is a proven tool for controlling and eradication life-threatening infectious diseases. In worldwide, between 2-3 million deaths yearly (Uddin, J et al., 2013).
A vaccine is a material extracted from the dead or microbes or can be a part of its protein component, and it used to provide active immunity to people against some infectious diseases (Liu, Zhou, Li, Garner, Watkins, Carter, & Albaiu, 2020). Vaccines possess an agent, comparable the disease-causing pathogens, and they are developed from weakened or killed microbes.
History of vaccination
According to Stanley A Plotkin (2005), In the laboratory of Louis Pasteur, the history of vaccination was beginning when Pasteur was doing studies of chicken cholera chicken cholera, In 1881. By accident Pasteur discovered the method that made the chicken immune against the cholera. Then, Pasteur hypothesed that via exposure the pathogens to environmental insults (ex; oxygen, chemicals and high temperature), the pathogens could be attenuated. Pasteur confirmed this hypothesis by discovered vaccines to anthrax and rabies.
In the next century, Calmette and Guérin utilized an artificial media to make an attenuated Mycobacterium bovis6 strain. Furthermore, Theiler used the mice and chick embryos to attenuate yellow fever virus (Theiler, M. & Smith, H. 1937). Respectively, Paul Ehrlich and Ilya Metchnikoff developed the concept of antibodies and cellular immune responses. consequently, the vaccinologists focused on stimulating these responses (Stanley A Plotkin. 2005).
The types of vaccines
Vaccines have several basic types.
Live Attenuated Vaccines:
attenuation leads to produce of live attenuated vaccines or with reduced virulence. Liu et al., (2020), highlight that this type of the vaccines able to mimic a real infection and the pathogen into the vaccine can reproduces inside the host, resulting to produce cellular, as well as humoral, immunity. Live attenuated vaccines create lifelong immunity, particularly in the viruses’ infections, and these types of the vaccines perhaps make long-term effectiveness because the attenuated pathogens can replicate in the host body (Tortora et al., 2009).
However, attenuated vaccines have cons and risk: the attenuated pathogens perhaps mutate which causes illness in the host. Immunosuppress people should not receive live vaccines because the attenuated pathogens may cause infections (Tortora et al., 2009).
Inactivated Killed Vaccines
In this type of vaccines, the whole killed pathogens were used. After the pathogens being grown in the laboratory, killing them is occurred via formalin or phenol. In this method, the pathogen lost the ability to replicate inside the host, but it is still able to stimulate the immune system to recognize it. Inactivated killed vaccines are safer than live vaccines. However, there are one risk associates with this type of the vaccines, that is incompleting the inactivation. Because of the inactivated killed vaccines are not able to replicate within the host cells, they often require to repeated booster doses. Mostly, this type of the vaccines induces humoral antibody immunity while the attenuated vaccines can induce cellular immunity (Tortora et al., 2009).
Subunit Vaccines
Subunit vaccines include fragments of the pathogens that are selected to induce an immune response. This avoids the risks that associated with the previous types (Live attenuated vaccines and Inactivated killed vaccines). Indeed, the subunit vaccines can be created by modify the genetic of other non-pathogenic microbes to produce the desired antigenic fraction, these vaccines are named recombinant vaccines, such as the hepatitis B vaccine. Hepatitis B vaccine consists of a protein of the coat of the virus which is produced via a genetically modified yeast, such as toxoid vaccines and polysaccharide vaccines (Tortora et al., 2009).
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The effect of vaccines on disease eradication
In Fact, vaccines are considered amongst the most, if not the most, effective medical development because they have successfully eliminated of several number of infectious diseases that once claimed millions of lives (LIU.M. 2003). Since 1997, not a single naturally acquired smallpox case has been reported in any place (Stanley A Plotkin, 2005). After the global victory over smallpox, the approach to eradicate polio went into overdrive. Resulting, by over 95%, the number of cases were reduced worldwide. Unfraternally, there are several factors as cultural and religious resistance to vaccination which led to polio’s reappearance recently. The campaigns of the worldwide vaccination controlled more than 10 other major infectious diseases. For example, measles, mumps, rubella, typhoid, tetanus, diphtheria, pertussis, influenza, yellow fever, and rabies was controlled. Most of the pervious diseases affected most likely babies and young children (Owen et al., 2009). The successful of vaccines relied on the teaching the body to respond to the wild type pathogens, rather than curing directly the disease, as what the antibiotics usually do (LIU.M. 2003).
Furthermore, Vaccines against several other diseases are still needed as malaria, tuberculosis, and AIDS. Indeed, there are existing vaccines need more work; to improve the safety or efficacy, or to reduce the cost. According to WHO data, because of disease, millions of infants die, and these diseases could be prevented by existing vaccines (Owen et al., 2009).
Clinical trials of DNA vaccines
The goals of the different clinical trials were demonstrating the safety and tolerability of the candidate vaccines and exploring in humans the efficacy of DNA vaccines. The injection of the plasmid that DNA construct is tolerated well in terms of safety in the patients and rarely involves systemic toxicities. Currently, tested DNA vaccines do not appear relevant levels of integration inside the cellular DNA of the host. The early studies in humans as well as the pre-clinical studies in non-human still do not reveal increasing in anti-nuclear or anti-DNA antibodies. The scientists follow up potential symptoms and signs of autoimmunity, which resulting of DNA vaccination, in the participants in human trials of DNA vaccines. So, these giving no convincing evidence of autoimmunity developing in association with a DNA vaccine (LIU.M. 2003).
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Breakthrough vaccines and their potential effect on public health:
COVID-19 vaccines
Malaria vaccine
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Conclusion:
References
Liu, C., Zhou, Q., Li, Y., Garner, L. V., Watkins, S. P., Carter, L. J., … & Albaiu, D. (2020). Research and development on therapeutic agents and vaccines for COVID-19 and related human coronavirus diseases.
LIU. M. A., (2003). DNA vaccines: a review. Journal of Internal Medicine 2003; 253: 402–410.
Stanley A Plotkin. (2005). Vaccines: past, present and future.
Theiler, M., Smith, H.H. (1937). The use of yellow fever virus by in vitro cultivation for human
immunization. J. Exp. Med. 65, 787–800
Tortora, G. J., Funke, B. R., Case, C. L. (2019). MICROBIOLOGY AN INTRODUCTION. THIRTEENTH EDITION.
Owen, J.A., Punt, J., Stranford, S. A., Jones, P. P. (2009). Kuby Immunology.
Uddin, J., Sarma, H., Bari, T. I., Koehlmoos. T. P. (2013). introduction of New Vaccines: Decision making Process in Bangladesh.