On Tuesday, the FDA’s Vaccines and Related Biological Products Advisory Committee (VRBPAC) voted 19-2 to approve the use later this year of Covid-19 vaccines based on an Omicron variant sequence. One of us (P.A.O.) was among those voting “no.” It is possible these vaccines will be two-component designs that also include the current version. Will Americans soon be better protected against Covid-19?
The Covid-19 vaccines currently authorized for use in the U.S. are all based on the sequence of the original SARS-CoV-2 virus, which was obtained early in 2020. The virus has evolved over the past 30 months, creating variants that are either more infectious, or harder to counter by vaccination, or both. In late December 2021, the Omicron variant (BA.1) emerged, becoming the most dominant strain in the U.S. BA.1 has now been almost completely replaced by other Omicron-based variants. The BA.4 and BA.5 viruses currently account for 50% of all circulating strains. Earlier variants, like Alpha and Delta, have essentially vanished.