(WASHINGTON, D.C.) — Just off the heels of a surge of new infections and deaths attributed to Thanksgiving holiday travel, the U.S. surpassed 350,000 COVID-19-related deaths over the weekend.

The U.S. death toll stands at 351,580 as of early Monday and, according to Johns Hopkins University, the nation has documented over 20.6 million infections.

Health officials expressed concern that the numbers will continue to worsen due to Christmas and New Years gatherings.  A record number of people traveled for the holidays and police across the nation broke up several large parties — such as a lounge party in New York on Friday that was attended by over 300 people.

The TSA reported record high numbers of people flying by air over the Christmas and New Year holiday weekends and screened 1,192,881 people on Saturday. Sunday is expected to be the biggest travel day since the start of the pandemic.

Meanwhile, vaccine rollout remains slow in the U.S. as only four million COVID-19 vaccines have been administered, says the Centers for Disease Control and Prevention.

According to the CDC COVID Data Tracker, which tracks both the Pfizer/BioNTech and Moderna vaccines, reports 13,071,925 vaccine doses had been distributed and 4,225,756 have been administered, as of Sunday.