Pfizer’s modified booster secured an emergency use authorization (EUA) from the US Food and Drug Administration (FDA) for people aged 12 and older, while Moderna’s shot was given an EUA for use in individuals aged 18 and up.
The bivalent vaccines or ‘updated boosters’ contain two messenger RNA (mRNA) components of SARS-CoV-2 virus, one of the original strain of SARS-CoV-2 and the other one in common between the BA.4 and BA.5 lineages of the omicron variant of SARS-CoV-2.
The FDA said the BA.4 and BA.5 lineages of the omicron variant are currently causing most cases of COVID-19 in the US and are predicted to circulate this fall and winter. In fact, BA.5 accounts for over 88% of all new COVID cases in the US, according to data from the US Centers for Disease Control and Prevention (CDC).
Supporting evidence
In June, the FDA’s Vaccines and Related Biological Products Advisory Committee voted overwhelmingly to include an omicron component in COVID-19 booster vaccines.
For each bivalent COVID-19 vaccine, the agency said it based its decision on the totality of available evidence, including extensive safety and effectiveness data for each of the monovalent mRNA COVID-19 vaccines.
The regulator said it also relied on safety and immunogenicity data obtained from a clinical study of a bivalent COVID-19 vaccine that contained mRNA from omicron variant BA.1 lineage that is similar to each of the vaccines being authorized, and nonclinical data obtained using a bivalent COVID-19 vaccine that contained mRNA of the original strain and mRNA in common between the BA.4 and BA.5 lineages of the omicron variant.