What Is Bivalent Vaccine? New Moderna Omicron Covid Booster Explained

The new shot targets two separate strains of Covid-19 — the original version of the virus that emerged in the central Chinese city of Wuhan along with the BA.1 subvariant, the earliest version of omicron. Other versions of omicron, BA.4 and BA.5, are now more prevalent, but the virus is evolving faster than new vaccines can be formulated and tested, and this is the closest match available that has received clearance. Moderna has another shot available that targets the BA.4 and BA.5 subvariants, which has been ordered by the US, but not yet cleared.