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Challenges yet to resolve of SARS-CoV-2 vaccine development

10 July 2020
Challenges yet to resolve of SARS-CoV-2 vaccine development


Dr. Muhammad Torequl Islam :
Development of a vaccine is a lengthy and expensive process. Due to high attrition, it takes multiple candidates and long time to produce a licensed vaccine. The developers generally follow a linear sequence of steps due to the cost and high failure rates, with multiple pauses for data analysis or manufacturing-process checks.
Moreover, developing a vaccine rapidly requires a new pandemic paradigm, with a fast start and many steps executed in parallel before confirming a successful outcome of another step, hence resulting in high financial risk.
Use of next-generation sequencing and reverse genetics is helpful to cut the development time of most conventional vaccines during epidemics. The severe acute respiratory distress syndrome coronavirus 2 (SARS-CoV-2)'s vaccine also has some novel platforms.
However, development of a successful vaccine for it poses some challenges for instance-
(i)    The virus's spike protein is a promising immunogen for protection, however, optimizing antigen design is critical to ensure optimal immune response. There are still controversial talks behind the targeting the full-length protein or only the receptor-binding domain of this virus.
(ii)     The exacerbating lung disease due to SARS and the Middle East respiratory syndrome (MERS) is still controversial as it may also occur by antibody-dependent pathway. It can be associated with a type 2 helper T-cell (Th2) response. Thus, requiring a suitable animal model and critical safety monitoring in clinical trials.
(iii)    The protection should be inferred from experience with the previous species (e.g., SARS and MERS vaccines), those are yet to be established. Generally, the potential duration of immunity is unknown for a naturally acquired infection, whether a single-dose vaccine will be effective or not to be assured.
(iv)    It is difficult to predict where and when the outbreaks will occur and to prepare the trial sites to coincide with vaccine readiness for testing. If multiple vaccines are ready at a same time, it will be important not to crowd sites or burden countries and their ethics and regulatory authorities with multiple trials, which was seen with Ebola vaccines during the 2013-2016 outbreak.
(v)    Having a high-mortality rate, it is difficult to conduct randomized, controlled trials with placebo groups; in fact, other approaches that are scientifically feasible, they're also typically slow, therefore, it should be harder to interpret the obtained data.
(vi)    Many vaccine development organizations are new and are yet to establish financial mechanisms and instruments to support the vaccine development process, additional funding sources should be required to provide the needful supports for the development and scale-up the manufacturing processes. Many vaccine candidates will be developed as by-products alongside the established one, there will no global entity responsible for financing or ordering vaccines from these kinds of manufacturers.
(vii)    To establish a globally fair vaccine-allocation system, clinical and serologic studies should be required to confirm the populations with the highest risk. Although it's unlikely, if the pandemic appears to abruptly end before vaccines are ready, significant financial losses will be a critical component of future pandemic preparedness.

(Dr. Muhammad Torequl Islam is Assistant Professor, Department of Pharmacy, Life Science Faculty, Bangabandhu Sheikh Mujibur Rahman Science and Technology University. E-mail: [email protected])

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