CHARLOTTE, N.C. — Pfizer has begun a study comparing its original COVID-19 vaccine with doses specially tweaked to match the omicron variant.
Pfizer and its partner BioNTech announced the study on Tuesday.
COVID-19 vaccine makers have been updating their shots in case global health authorities decide a change is needed.
The Pfizer study will include 1,420 healthy adults.
Most already are vaccinated and will get boosters of the omicron-based vaccine or the original version.
Some unvaccinated volunteers will get three omicron-based doses.
The original vaccines still offer good protection against severe illness and death.
Studies have made clear that adding a booster dose strengthens that protection.
