President Joe Biden has tested positive for COVID-19, the White House announced on Thursday.

Biden received his first two doses of the Pfizer-BioNTech vaccine in December 2020 and January 2021, and received two Pfizer booster shots in September 2021 and March 2022, so his case is a so-called breakthrough infection.

Infections in fully vaccinated people have become increasingly common with the emergence of the Delta and Omicron variants, but the shots have proven effective in preventing serious illness, hospitalization, and death. 

The rapid global spread of Omicron, which was first detected and identified in southern Africa in November, caused a massive spike in coronavirus cases in the US beginning in early December that peaked in mid-January 2022 before leveling off.

While cases have significantly declined in recent months, Omicron and its BA.2 subvariant have continued to circulate in the Washington, DC area — and among its prominent politicians and power players. 

Vice President Kamala Harris announced that she tested positive on April 26, and dozens of members of Congress have reported contracting COVID-19 in the past several months.

Over 70 attendees of the prestigious Gridiron Club’s annual dinner, a well-heeled affair featuring Washington’s elite political figures and journalists, disclosed positive tests in the days after the April 2 event. 

Attorney General Merrick Garland, Commerce Secretary Gina Raimondo, Reps. Adam Schiff and Joaquin Castro, and  Harris’ communications director Jamal Simmons, all disclosed positive tests after attending the Gridiron dinner, which had over 600 guests in attendance. 

House Speaker Nancy Pelosi announced in early April that she tested positive for COVID-19 the day after attending a bill signing event at the White House where she and other members of Congress, all maskless, gathered around Biden for a photo. 

President Barack Obama, 2016 Democratic presidential nominee Hillary Clinton, Second Gentleman Doug Emhoff, and White House press secretary Jen Psaki, who had two breakthrough cases of COVID-19, have also tested positive for the virus in recent months.