Most of the COVID-19 infections in the U.S. traced to the Omicron variant so far have been mild illnesses in people who were vaccinated, the U.S. Centers for Disease Control said Friday.

According to the agency, in the first 43 cases Omicron variant cases that were investigated, 34 occurred in people who had completed their vaccinations, including some who had already taken their booster shots.

"The most commonly reported symptoms were cough, fatigue, and congestion or runny nose. One vaccinated patient was hospitalized for 2 days, and no deaths have been reported to date," the U.S. CDC said.

The agency noted that Case investigations have identified exposures associated with international and domestic travel, large public events, and household transmission.

The U.S. remains to be the hardest-hit country globally by the COVID-19 pandemic, having recorded 49,687,827 infections with 794,941 deaths.