DC Health confirmed the District’s first four cases of the Omicron COVID-19 variant on Sunday.

All four cases are adults who were fully vaccinated, one of whom did not receive a booster shot while the other three people’s booster statuses were unknown, according to the release. DC Health said all residents 16 and older whose second dose was more than six months ago should get their booster shot “as soon as possible,” also encouraging everyone five and older to get vaccinated.

“The recent emergence of the Omicron variant further emphasizes the importance of vaccination, boosters and prevention strategies (e.g. masking, washing your hands frequently, choosing activities wisely, and physically distancing from others) needed to protect against COVID-19,” the release reads.

City officials said one of the Omicron cases is a woman who recently traveled to New York and Florida. Two of the other cases are women who traveled during Thanksgiving to Maryland and Virginia, respectively, but the man identified as the fourth case had no known travel, exposures or close contacts.

Individuals who were named as close contacts have been notified, DC Health said.

The World Health Organization classified the Omicron mutation as a “variant of concern” late last month.

The Omicron variant has been found in more than two dozen states including Virginia, which detected its first case of the new variant on Thursday, and Maryland, which identified its first three cases earlier this month.

Officials have been conducting genetic sequencing on COVID-19 cases identified through GW’s in-house testing lab but have not yet attributed any positive cases at GW to the Omicron variant.

DC Health said anyone in the District who is six months and older should also get the flu vaccine to stay safe.

Residents looking to receive a COVID-19 vaccine can schedule an appointment at a local pharmacy on vaccines.gov, visit a D.C. government walk-up location or call 1-855-363-0333 to request vaccination at home, according to the release.

The Medical Faculty Associates is offering walk-in appointments across from the GW Hospital at 949 23rd St. NW from 7:30 a.m. to 3:30 p.m. on all weekdays.