Pfizer opens study of COVID shots updated to match omicron

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.