Image by Gerd Altmann from Pixabay 

Article Writer-   Ayesha Naseem K , B.Sc., Zoology, Aligarh Muslim University(AMU), Uttar Pradesh (India)


he development of vaccines has played an extremely important role in fighting infectious diseases. They have markedly reduced the targeted infectious disease in all the documented examples. The eradication of smallpox has been one of the major achievements of the vaccine. This was possible because smallpox was almost always clinically apparent and therefore could be vaccinated at exposure to the contacts of a case-patient. This is not always the case though. Despite the impressive results made with vaccines such as measles, rubella, and meningitis, there are still many existing shortcomings in producing vaccines that are desperately needed. The success of vaccines currently available depends on their ability to induce antibodies that block or neutralize infectious agents or their products. Developing an effective vaccine faces various medical, logistical, and social challenges. One of the researchers’ greatest challenges is the uncertainty about the criteria for sufficient immunity against both infection and disease.

 The development of new and effective vaccine products cannot progress without a thorough knowledge of the immune protection correlates as it provides essential information for the design of rational vaccines and also guides the parameters to be measured when evaluating the effectiveness of the vaccines. The collection of such data usually depends on having material from patients who have recovered from a natural infection and on the availability of an animal model that responds to the infection and the formulation of the vaccine in a manner similar to humans. This can be tackled by creating more specific animal models, gathering and testing more human samples, and increasing the use of human challenge infections in the experimental process.

 A whole other challenge is the lack of information regarding the intended vaccine recipients’ infectious exposures. The recognized immunodominant antigens and the protective immunity mechanisms displayed in animal models such as mice, guinea pigs, and rabbits can differ significantly from humans. Animal studies are useful but can not be a complete substitute for human trials. More human samples need to be collected and analyzed.

 There are significant ethical questions surrounding the enrolment of people in these trials. Volunteers must be made aware of the risk of immunization seropositivity, and the potential complications that may result from insurance eligibility, employment, and immigration.

 The development of vaccines would be greatly assisted by the existence of a suitable and practical animal model in which scientists could study pathogenesis and investigate chemotherapy drugs. These models would also allow researchers to study the effectiveness of the vaccine when faced with various viral challenges. Consequently, vaccine testing and development also take time due to the lack of an effective animal model.

 One cannot neglect the market when considering vaccine development. Often only a single company produces a new vaccine, and thus price competition is not a driver to reduce costs. This could limit access to effective vaccines, particularly in developing countries where cost-benefit analysis may be the primary influence relative to poorer countries where affordability is the deciding factor.

The high costs of developing vaccines lead to the premature abandonment of potentially useful products. Vaccine manufacturers face a high-cost and high-risk business environment, competition with other major vaccine manufacturers, increased expectations for compliance and safety, and highly sophisticated technology-driven platforms. It usually takes 12–14 years to create and approve a vaccine drug.

 Research is often hampered by a lack of understanding of the immune responses specifically necessary for protection, or by a lack of approved adjuvants and delivery systems to induce the reactions needed. Vaccines are to be used in populations with less reactive immune systems for effective outcomes. To achieve this, a deeper understanding of the mechanisms of action of adjuvants currently used is indispensable and vaccine delivery systems are to be established, specifically for use in populations with immunocompromise.

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