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Why will it take so long for a coronavirus vaccine to be ready?

To date, career public servant-scientists at the US Food and Drug Administration (FDA) have granted Emergency Use Authorizations (EUAs) for the Pfizer-BioNTech, Moderna, and Johnson & Johnson COVID-19 vaccines. (Note: On Tuesday, April 13th, 2021, the FDA and Centers for Disease Control and Prevention advocated to pause the use of the Johnson & Johnson coronavirus vaccine "out of an abundance of caution." For more information, click here.) Before the EUAs were granted, independent experts serving on the FDA's vaccine advisory committee had voted overwhelming that, for people 16 years old and above (Pfizer-BioNTech), or 18 years old and above (Moderna and Johnson & Johnson), the benefits of the vaccines outweigh the risks. Canada and Britain have also cleared the Pfizer-BioNTech COVID-19 vaccine for use. There are limited doses of the vaccines, and it is expected the vaccines will first be made available to those considered most at risk to COVID-19 - health care workers and residents of long-term care facilities - although this will differ by state. For more information on the Pfizer-BioNTech COVID-19 vaccine, check out this nice FAQ from NPR. To read the FDA's fact sheet on the Moderna COVID-19 vaccine, click here and for the fact sheet on the Johnson & Johnson COVID-19 vaccine, click here.

Vaccine development takes a long time because there are many steps in the process. Researchers must ensure the vaccine is safe, causes the correct immune response without causing other problems, and is protective against COVID-19. There are many stages of tests both in the lab and then clinical trials. Usually those must be completed before wide scale production of vaccine doses can begin, but some vaccine-makers have engaged in "at-risk manufacturing," producing vaccine candidate doses without knowing whether the vaccine candidates will succeed in trials. In the past, this process has taken years, but experts are cautiously optimistic that a COVID-19 vaccine will be available in limited quantities toward the end of 2020, and more widely accessible to the general population by mid to late 2021.

Updated 13 April 2021