Pfizer has begun a study comparing its original COVID-19 vaccine with doses specially tweaked to match the hugely contagious omicron variant.

Pfizer and its partner BioNTech announced the study on Tuesday.

COVID-19 vaccine-makers have been updating their shots to better match omicron in case global health authorities decide the change is needed.

Omicron is more likely than previous variants to cause infection even in people who’ve been vaccinated, but it’s not yet clear that a change to the vaccine recipe will be ordered. Among the issues regulators are weighing: Some of the first places to face an omicron surge already are seeing the mutant wane — and there’s no way to know if the next variant that arises will resemble omicron or be totally different. Continue Reading