Three vaccines developed to prevent COVID-19 infections received emergency use authorization earlier this year, allowing nearly half the U.S. population to be fully vaccinated against the virus.
But while much of the population remains skeptical of vaccination, the U.S. Food and Drug Administration is working to fully approve, or license, the three vaccines.
Some experts say that this approval, which is a much longer and more complicated process, may encourage some skeptics to get vaccinated.
"We recognize that for some, the FDA approval of COVID-19 vaccines may bring additional confidence and encourage them to get vaccinated," Dr. Peter Marks, the director of the Center for Biologics Evaluation and Research at the FDA, told VOA via email.
But experts have said repeatedly that the three vaccines — Pfizer, Moderna and Johnson & Johnson — had been declared safe and effective before they were authorized for emergency use.
"The full approval process has less to do with getting additional scientific evidence and more to do with some of the logistics," said Dr. David Dowdy, an epidemiologist at the Bloomberg School of Public Health at Johns Hopkins University. He told VOA the process included steps such as specifying the labeling of the vaccine and the specific wording on packaging.
Currently, Pfizer and Moderna have each filed a biologics license application (BLA) — the last step to full approval — with the FDA. Johnson & Johnson said in a statement released earlier this year that it would apply "later in 2021."
What is the normal FDA licensing process for vaccines?
After a vaccine is developed, drugmakers usually test them on animals and tissue samples in preclinical trials.
Once a vaccine passes these pretrials, it undergoes three phases of clinical trials in humans, each trial with an increased number of participants. During this monthslong period, FDA officials will monitor the progress of the trials, observe the vaccine's long-term efficacy and look for rare side effects.
Only after these trials are completed can a drug company submit a biologics license application, the formal and final approval process for a vaccine.
Once this application is submitted, the FDA will review all information from the clinical trials and inspect every facility where the vaccine is made to ensure everything is in order.
How will the process for the COVID-19 vaccines be different?
Three COVID-19 vaccines have already been widely used throughout the U.S. and the world because they were given emergency use authorization.
Still, all vaccines must go through the process of full licensing, which can take years. The FDA has not specified how long this process will take but has said that the COVID-19 vaccines are being given "priority review."
"Acknowledging the urgency related to the current state of the pandemic, we have taken an all-hands-on-deck approach, including identifying additional resources, such as personnel and technological resources from across the agency, and opportunities to reprioritize other activities, in order to complete our review to help combat this pandemic surge," Marks said.
The FDA clarified that a "priority review designation" means it aims to fully license vaccines within six months of an application being filed, as opposed to the standard 10 months.
According to Dowdy, the only differences between licensing a COVID-19 vaccine versus previous vaccines will involve speed and manpower. Dowdy likened the process to getting a passport, saying that while passport processing can take months because of the volume of applications, people can apply to expedite the process. This does not make the process less rigorous; it just means that a certain application is moved to the front of the line.
"We're not giving these vaccines a free pass just because they're being manufactured in the midst of a pandemic. The goal is to try and expedite these processes as much as possible," he said.
How is emergency use authorization different?
Three COVID-19 vaccines were granted emergency use authorization earlier this year. Such approval requires the same scientific evidence and number of clinical trials proving the safety and effectiveness of the vaccine, but it skips some steps and technicalities concerning labeling and distribution.
"Although an authorization is not an FDA approval, the FDA conducted a thorough scientific evaluation of each of the authorized vaccines and can assure the public and medical community that the vaccines meet FDA's rigorous standards for safety, effectiveness and manufacturing quality," an FDA official told VOA via email.
Experts stress that millions of people have received the vaccines and that data continue to support their safety and effectiveness against the coronavirus.