Pfizer/BioNTech have initiated an application for full FDA approval of its COVID-19 vaccine booster shot for individuals aged 16 and up, the companies announced Wednesday, noting plans to complete the application later this week.

The request for the so-called supplemental biologics license application draws on Phase 3 clinical trial data among 306 participants aged 18 to 55 who received a third dose between 4.8-8 months following the initial two-dose series, with some 2.6 months of follow-up. The companies said levels of neutralizing antibodies were 3.3 times higher following the third dose, versus the second dose.

MODERNA WRAPS FULL FDA APPROVAL REQUEST OF COVID-19 VACCINE

Side effects within a week after the booster were mild-to-moderate, the companies said, with most frequent side effects including "injection site pain, fatigue, headache, muscle and joint pain, and chills," similar to the second dose of the primary series.

Pfizer/BioNTech plan to submit the findings to peer-reviewed journal and will share the data with regulatory agencies worldwide in the weeks ahead. 

FDA APPROVES PFIZER'S COVID-19 SHOT: WHAT IS LICENSURE?

While most Americans may become eligible for a third dose of mRNA vaccine next month, pending FDA review, a small fraction of the U.S. population ages 12 and older with weakened immune systems (i.e. immunocompromised patients) became eligible for a third dose of Pfizer or Moderna COVID-19 vaccine earlier this month.