The two updated booster shots aimed at providing "better protection against Covid-19 caused by the Omicron variant" are approved for people age 12 and above for the Pfizer shot and 18 and older for Moderna, the Food and Drug Administration (FDA) said in a statement.

This new generation of anti-Covid vaccines targets both the original strain of coronavirus and the BA.4 and BA.5 lineages, the subvariants of Omicron that are causing the most cases in the United States and which the FDA predicts will circulate in the coming months.

Earlier this summer the US health department announced it had purchased 105 million doses from Pfizer and 66 million from Moderna for use over the fall and winter.

The vaccines have yet to be recommended by the Centers for Disease Control and Prevention, the nation's health protection agency. But an independent panel of experts is scheduled to be convened by the CDC on Thursday to discuss the updates. 

CDC director Rochelle Walensky will be in charge of giving the final green light.

The new versions of the vaccines could potentially be available in the United States as early as next week.