Full FDA Approval vs EUA for Vaccines : What’s Different?

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The US FDA is preparing to issue full approvals for COVID-19 vaccines, but how does a full FDA approval differ from the current EUA (Emergency Use Authorisation)?

Updated @ 2021-08-21 : Added more details about the advantages of the full FDA approval.

Originally posted @ 2021-08-18


FDA Approval for Vaccines : The Usual Process

First, it is important to get a quick understanding of what’s the usual process for a full FDA approval for vaccines and other drugs.

Full FDA approval for a new vaccine (or drug) is only given after a multi-step process :

  1. Preclinical safety tests on animals.
  2. An investigational new drug application (IND) outlines the proposal for human testing in clinical trials.
  3. Phase 1 safety studies, which typically involve 20 to 80 people.
  4. Phase 2 efficacy studies, which typically involve a few dozen to about 300 people.
  5. Phase 3 randomised, controlled studies, which typically involve several hundred to about 3,000 people.
  6. The FDA and vaccine sponsors will meet to discuss the results during the pre-NDA period, before a new drug application (NDA) is submitted.
  7. Submission of an NDA is the formal step asking the FDA to consider the vaccine for marketing approval.
  8. After an NDA is received, the FDA has 60 days to decide whether to file it so it can be reviewed.
  9. If the FDA files the NDA, an FDA review team is assigned to evaluate the sponsor’s research on the vaccine’s safety and effectiveness.
  10. The FDA reviews information that goes on a vaccine’s professional labeling (information on how to use the drug).
  11. The FDA inspects the facilities where the vaccine will be manufactured as part of the approval process.
  12. FDA reviewers will approve the application or issue a complete response letter.


Full FDA Approval vs EUA for Vaccines : What’s Different?

As the US FDA prepares to issue full approvals for COVID-19 vaccines, you may be wondering – how does a full FDA approval differ from the current EUA (Emergency Use Authorisation)?

Many people point out that the EUA is an authorisation for “unapproved medical products or unapproved uses of approved medical products“.

That is the definition of the EUA, but not the substance. Here are the facts…

Same Approval Process

That vaccines approved by EUA actually undergo the same FDA approval process outlined above!

The biggest difference is the post-study follow-up that is required :

  • EUA : At least half of the participants in the studies must be followed for at least two months after vaccination.
  • Full FDA Approval : All of the participants in the studies must be followed for at least six months.

Since the vast majority of side effects occur right after vaccination, the shorter 2-month follow-up is sufficient for an EUA, especially in the context of an emergency like the COVID-19 pandemic.

The longer follow-up for the full FDA approval will provide more data on its safety, and give reviewers time to examine the reported adverse effects.

FDA Approval vs EUA for Vaccines : What's The Difference?

More Manufacturing Details + Inspections

For a full FDA approval, the vaccine manufacturer must also provide more detailed manufacturing plans and processes.

The US FDA also takes the extra time to increase oversight and inspection of those manufacturing facilities.

Public Marketing

Manufacturers that only received an EUA for their vaccines are not allowed to market them to the public.

A full FDA approval is required before they can market their vaccines to the public.


FDA Fast Track Approval For Vaccines : Does It Compromise Safety?

Pfizer and Moderna started their “rolling submission” for full approval under the US FDA Fast Track process in May 2021 and June 2021 respectively.

There are fears that this US FDA Fast Track status lets them bypass rigorous checks, and put people’s lives at risk.

The truth is the US FDA Fast Track process is only open to certain drugs (including vaccines) that demonstrate these advantages :

  • Showing superior effectiveness, effect on serious outcomes or improved effect on serious outcomes
  • Avoiding serious side effects of an available therapy
  • Improving the diagnosis of a serious condition where early diagnosis results in an improved outcome
  • Decreasing a clinical significant toxicity of an available therapy that is common and causes discontinuation of treatment
  • Ability to address emerging or anticipated public health need

It is also not a shortcut in the approval process, because the process involves more engagement with the FDA, not less :

  • More frequent meetings with FDA to discuss the drug’s development plan and ensure collection of appropriate data needed to support drug approval
  • More frequent written communication from FDA about such things as the design of the proposed clinical trials and use of biomarkers
  • Eligibility for Accelerated Approval and Priority Review, if relevant criteria are met


It also allows for the rolling review of the vaccine or drug, as parts of the application are completed/

  • Rolling Review, which means that a drug company can submit completed sections of its Biologic License Application (BLA) or New Drug Application (NDA) for review by FDA, rather than waiting until every section of the NDA is completed before the entire application can be reviewed. BLA or NDA review usually does not begin until the drug company has submitted the entire application to the FDA

Think of the rolling review as a long exam, during which you hand over sections that you have completed to the examiner to mark, while you work on the rest.

The FDA Fast Track process is meant to expedite the evaluation process for important drugs or vaccines, without compromising their safety or efficacy.


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Dr. Adrian Wong has been writing about tech and science since 1997, even publishing a book with Prentice Hall called Breaking Through The BIOS Barrier (ISBN 978-0131455368) while in medical school.

He continues to devote countless hours every day writing about tech, medicine and science, in his pursuit of facts in a post-truth world.


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