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Published on April 23, 2021

COVID-19 vaccine developed quickly without sacrificing safety

It can take 10 years or longer for a vaccine to reach FDA approval in the United States. So, how did the COVID-19 vaccines get through the process faster without compromising safety or skipping any steps?

COVID-19 vaccine development timeline

Here are 5 factors that led to the fast-tracked timeline:

Coordination and funding

In response to the COVID-19 pandemic, partnerships were formed between government agencies, non-profit organizations and pharmaceutical companies—nationally and internationally—to develop a coordinated strategy and secure billions of dollars in funding (e.g., Accelerating COVID-19 Therapeutic Interventions and Vaccines (ACTIV) and Operation Warp Speed).

mRNA technology and adenovirus-vector vaccines

mRNA vaccines are faster to produce in large amounts than traditional vaccines. They shift some of the work out of the lab and into your body. The mRNA COVID-19 vaccines provide instructions that teach your immune system what the virus looks like and how to protect you from infection. While no other licensed vaccines currently use mRNA, the science has been building for over a decade.

The extra prioritization and funding allowed these vaccines to get to the finish line faster. Adenovirus-vector vaccines have some similarities to mRNA vaccines. Instead of mRNA carrying the instructions to teach your body how to protect against infection, it uses a harmless virus to carry the code. Your immune system takes care of the rest. Adenovirus-vector vaccines have been successfully made before against Ebola.

Phases of clinical trials overlapped

A typical vaccine development timeline is linear and each step is completed before going to the next. With the COVID-19 vaccine, some steps overlapped including clinical trials (e.g. phase two trials started before phase one trials were finished, though each was completed in its entirety). 

Manufacturing started while clinical trials were underway

Manufacturing of the COVID-19 vaccine started while clinical trials were still underway. Normally, vaccine manufacturing doesn't begin until after all trials are complete.


Due to this unprecedented public health emergency, the FDA and CDC prioritized review, authorization and recommendation of COVID-19 vaccines.

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