COVID-19 cases are seeing a surge in the U.S. caused by the delta variant and booster shots are more crucial now than ever.
The omicron variant has been detected in at least 29 states and D.C.
Top U.S. officials say the latest data on omicron is showing that it is spreading very easily, but it is still unclear if it leads to milder disease.
Either way, experts say boosters are critical.
"Preliminary data showed that when you get a booster, for example, the third shot of an MRNA, it raises the level of protection high enough that it does then do well against the Omicron," says Fauci.
Some states are now reinstating mask mandates to prevent the spread of the virus.