Pfizer-BioNTech seeks FDA approval for third dose of its COVID-19 vaccine

Pfizer-BioNTech announced on Wednesday it is seeking approval from U.S. regulators for the third dose of its COVID-19 vaccine which they are now referring to by its brand name: Comirnaty. 

Last week, the U.S. Food and Drug Administration authorized an additional COVID-19 booster vaccine for people who have compromised immune systems.

Immunocompromised people can include organ transplant recipients, cancer patients, or people with other conditions. The U.S. Centers for Disease Control and Prevention has previously identified people with severely weakened immune systems as being at higher risk for getting severely ill from COVID-19, more likely leading to hospitalization or death.

About 3% of the U.S. adult population is immunocompromised, according to the CDC

In the most recent announcement from Pfizer-BioNTech, they cited data from a phase 3 trial consisting of 306 participants who received the third dose of their Comirnaty vaccine. The participants were inoculated with the third shot between 4.6 and 8 months after getting their two doses. 

Results from the trial determined that the boosters offered participants protection three times higher than the second dose. 

RELATED: Full FDA approval of COVID-19 vaccines could spur more company, university mandates

The request for federal approval of a booster shot by Pfizer-BioNTech comes days after the FDA granted full approval of their COVID-19 vaccine — now known as the Comirnaty vaccine — for people aged 16 and older. 

The new name for the Pfizer COVID-19 vaccine comes from Brand Institute, the pharmaceutical naming company that worked with Pfizer-BioNTech to come up with "Comirnaty." 

According to a news release from the Brand Institute, the name is a mash-up representing "a combination of the terms COVID-19, mRNA, community and immunity."

RELATED: Comirnaty: Pfizer-BioNTech explains COVID-19 vaccine name’s meaning

Vaccines are that are mRNA, or messenger RNA, teach cells to develop a protein to fight a virus, rather than using an inactivated germ to fight off an infection.

More than 200 million Pfizer doses have been administered in the U.S. under emergency provisions — and hundreds of millions more worldwide — since December. In going a step further and granting full approval, the Food and Drug Administration cited months of real-world evidence that serious side effects are extremely rare.

Pfizer said the U.S. is the first country to grant full approval of its vaccine, in a process that required a 360,000-page application and rigorous inspections. Never before has the FDA had so much evidence to judge a shot’s safety.

The delta variant has sent cases, deaths and hospitalizations soaring in recent weeks in the U.S., erasing months of progress. Deaths are running at about 1,000 a day on average for the first time since mid-March, and new cases are averaging 147,000 a day, a level last seen at the end of January.

As for effectiveness, six months into Pfizer’s original study, the vaccine remained 97% protective against severe COVID-19. Protection against milder infection waned slightly, from a peak of 96% two months after the second dose to 84% by six months.

Those findings came before the delta variant began spreading, but other data from the Centers for Disease Control and Prevention shows the vaccine is still doing a good job preventing severe disease.

This story was reported from Los Angeles. The Associated Press and Chris Williams contributed.