- Phase 1 trials are based on dosage to test the strongest immune response without serious side effects (generally non-randomized)
- Phase 2 the evaluation is expanded and volunteers are separated by sex, age, health, and status
- Phase 3 thousands of candidates are given the vaccine, the results are then submitted to the WHO to be judged

Clinical Trials 

- s564 of the US Federal; Food, Drug, and Cosmetic Act permits the commissioner of the FDA to remove some regulatory hurdles for a drug on the grounds of a public health emergency.
- Side effects of a "successful vaccine" aren't known and cannot be studied without given time
- Each day the vaccine is delayed to the distribution billions of dollars of economic damage is caused 
- Use of patents and the delay it may cause on distribution

Repercussions of a "successful vaccine"

- Transitioning from animal testing to human clinical trials
- The resources needed to produce a vaccine
- The duration and magnitude of the immunity provided by a potential vaccine

University of California, Santa Cruz

Includes the scientific challenges and direction the development of COVID-19 vaccines.
- Challenges of development
- Vaccine antigen selection and design 
- Protective immunity 
- Preclinical evaluation of safety
- Manufacturing 
- Vaccine design itself is complicated
- Need for cold chain
- Consideration of cost
- Global distribution
-Authorization by US Food and Drug Administration and VRBAC
- Goals of development

Development of COVID-19 Vaccines

Chen, W. (2020). Promise and challenges in the development of COVID-19 vaccines. Human Vaccines & Immunotherapeutics, 1-5. doi:10.1080/21645515.2020.1787067

Promise and challenges in the development of COVID-19 vaccines

Vaccine development comes with a host of problems that slows down the progression of producing one. Aside from the economic and time-sensitive factors, vaccines come with alternative effects that need to be studied and approved by national organizations (FDA) for general use:
- Antibody-dependent-enhancement (ADE)
- Comorbidities 
- Challenge studies

Challenges to vaccine development

The majority of COVID-19 vaccine candidates target the spike protein and receptor-binding domain of the virus. This is because the spike protein binds to the ACE2 receptor on the surface of host cells.
Other structural antigens targeted are the envelope, membrane, and nucleocapsid proteins of the virus with studies identifying B and T epitopes being done currently.

Vaccine antigen selection and design

A viable vaccine should provide the host long-lasting immunity without side-effects by neutralizing the S protein of the virus through a balanced T-cell and antibody immunologic response. 
The goal is to avoid the current immunologic response of producing a cytokine storm without encountering ADE specific challenges.

Protective Immunity

Preclinical evaluation of vaccine efficacies and safety

- manufacturer engagement in developing vaccine
- regulating organizations
- cold chain
- various production platforms

Factors involved in Manufacturing

It might not take until 2024 to get a full safe vaccine for COVID-19. There may not be enough to treat everybody since two rounds are going to be needed to gain full immunity. The two rounds of the vaccine will be given a month apart. The FDA is hoping to come out with a vaccine by October to have as a temporary one. 

Global Distribution 

- herd immunity against the SARS-CoV-2 virus

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