April 12, 2024

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The development of vaccines for emerging infectious diseases

The development of vaccines for emerging infectious diseases

The development of vaccines for emerging infectious diseases.  Throughout human history, new and re-emerging infectious viral diseases have been threatening mankind.

High-density urbanization is conducive to high-density flow of people through various modes of transportation. Large gatherings, changes in human behavior, changes in the environment and ecosystems, and imperfect global public health mechanisms have accelerated the emergence and spread of animal viruses, making them a threat to human survival.

In 1918, the “Spanish flu” killed nearly 40 million people. As of April 20, 2021, the COVID-19 virus has also claimed more than 3 million lives.

In addition to blockade, the only control method is limited to a series of mitigation measures: self-isolation, wearing masks, restricting travel, avoiding gatherings, etc.

These measures are not perfect and have certain limitations. These reasons force researchers and policy makers to remain vigilant, to re-examine the methods of investigating and managing emerging infectious disease threats, and to re-examine the global mechanism for pandemic control

The following table is a partial list of newly emerged viral infectious diseases from 1900 to 2020:

The development of vaccines for emerging infectious diseases


Vaccine development model for emerging infectious diseases

Over the past two decades, people’s awareness of emerging infectious diseases has continued to evolve. Looking back at the SARS-CoV outbreak in 2002, it can be seen that although the number of deaths and infections is small, its high mortality and transmission have caused major global chaos. With the start of the vaccine work, the epidemic ended abruptly. Since then, the spread of civet cats to humans has also stopped. As a result, the vaccine work against SARS-CoV ended and its funding was cut. Only one fully inactivated vaccine and one DNA vaccine have undergone phase I clinical trials.

According to the traditional research and development process, it takes 5 to 10 years to develop a vaccine against infectious pathogens. This method does not meet the needs of new pathogens during epidemics. The figure below shows a comparison of the epidemic curve and the vaccine development schedule.

The development of vaccines for emerging infectious diseases


From the sequencing of the first SARS-CoV-2 virus to the interim analysis of the vaccine efficacy test, the entire R&D pipeline was completed in less than 300 days. From these shortcomings in vaccine development under public health emergencies, there has been the Epidemic Preparedness Innovation Alliance (CEPI), a non-profit organization dedicated to developing vaccine capabilities in a timely manner, in anticipation of epidemics. CEPI initially focused on diseases selected from the WHO EID priority pathogen list-Middle East Respiratory Syndrome (MERS), Lhasa Fever, Nipah, Rift Valley Fever (RVF) and Chikungunya. The goal of the center is to advance vaccine candidates to the second stage and prepare vaccine stocks for use/testing in pandemic situations. CEPI has also prepared for “Disease X” by investing in innovative rapid response platforms that can move from sequence to clinical trials in weeks instead of months or years, such as mRNA and DNA technologies. COVID-19 was declared a global health emergency in January 2020, and it was put into use during the pandemic in March 2020.


Vaccine platforms and vaccines for emerging infectious diseases

Table 2 below lists the most important technical vaccine platforms for vaccines developed or under development for emerging viral infectious diseases.

The development of vaccines for emerging infectious diseases


Although the COVID-19 mRNA vaccine is a good concept, it still requires more work and time to gather experience from its large-scale deployment and effectiveness studies.

While several DNA vaccines are licensed for veterinary applications, and DNA vaccines have shown safety and immunogenicity in human clinical trials, no DNA vaccine has reached the license for human use.

Recombinant proteins have very different designs for the same pathogen (for example, subunits, virus-like particles), and are usually formulated with adjuvants, but have a longer development time. The virus-like particle vaccine used for hepatitis B and human papillomavirus is safe, highly immunogenic, effective, and easy to mass produce. The technology is also easy to transfer.

The entire inactivated pathogen (such as SARS-CoV-2, polio, cholera) or live attenuated vaccine (such as SARS-CoV-2, polio, chikungunya) is unique to each pathogen. Depending on the pathogen, these vaccines may also require biosafety level 3 production (at least COVID-19 and polio), which may limit the possibility of technology transfer to increase global production capacity.


Pharmacovigilance and surveillance

Taking into account the urgency of public health and the foreseeable and extensive vaccination campaigns on a global scale, the EMA and the national authorities of the EU member states have prepared for the expected high data volume and have formulated a specific vaccine Pharmacovigilance plan. Good pharmacovigilance practices include detailed requirements and guidance on the principles and requirements of the vaccine risk management plan (RMP). In addition, the core RMP requirements for the COVID-19 vaccine have also been formulated to promote and standardize the preparation of RMPs by enterprises and their evaluation by personnel.

The preparation of the RMP addresses the planning of the marketing authorization holder for the safety tracking of the COVID-19 vaccine after authorization, while acknowledging the uncertainty in the pandemic environment, and recommending methods for preparing for medical alert activities. Similarly, the American Advisory Committee on Immunization Practice (ACIP) initially held a COVID-19 vaccine safety technical working group meeting in June 2020 to provide the ACIP COVID-19 vaccine working group and the entire ACIP on the safety of the COVID-19 vaccine under development. Recommendations approved after sexual monitoring and pharmacovigilance.


How to produce more vaccines faster?

It is unprecedented to produce and sell hundreds of millions of doses of COVID-19 vaccine within a year after the identification of the generalized pathogen. Although the principle is simple, the manufacturing equation is complicated and easy to delay. The technology platform (mRNA, fully inactivated virus, vector, protein with or without adjuvant), dosage (low dose, medium dose, high dose), vaccination schedule (single or double dose) and manufacturing of vaccines The capacity, production capacity and reputation of the supplier are all important considerations for regulators and the WHO. The initial stage of scale-up of production will be a key regulator of vaccine acquisition. This may be affected by vaccine nationalism and announced bilateral agreements between manufacturers and high-income countries. Companies such as Sinopharm Group, India Serum Institute or Bharat have huge production capacity, but they must supply the huge markets of China and India. There have been reports of delays in the production of some Western and Chinese COVID-19 vaccines.


Lessons from COVID-19

Finally, what the author wants to say is that the lessons learned from the COVID-19 pandemic need to be sorted out and applied to the development of vaccines for emerging infectious diseases and new pandemic pathogens in the future.

The long-term threat of emerging pathogens requires vigilance, supervision and preparation for the development and deployment of vaccines, and all cross-cutting activities need to be between epilogists, scientists, developers, human and veterinary health authorities, regulators, and funders It goes perfectly.

Global health stakeholders have learned something in the effective development of vaccines: they still have a lot to learn when manufacturing and using vaccines, taking into account fairness and accessibility.


(source:internet, reference only)

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