"I regularly test for COVID & while I tested negative earlier this week, today I tested positive with a breakthrough case. Thankfully, I am only experiencing mild symptoms & am grateful for the protection provided against serious illness that comes from being vaccinated & boosted," Warren said on Twitter on Sunday.
The former Democratic presidential candidate also urged Americans to get the vaccine and the booster shot as soon as possible.
US President Joe Biden is expected to deliver a national speech on Tuesday addressing issues relating to the Omicron strain of the coronavirus, which emerged in South Africa in November and has been declared a variant of concern by the World Health Organization (WHO).
On December 2, Biden announced the federal government plan to combat COVID-19 and the new Omicron variant over the winter months, during which coronavirus cases are expected to rise in the US.
The winter plan includes measures to expand nationwide vaccine and booster outreach, improve COVID-19 testing access, bolster the government’s response teams and accelerate efforts to vaccinate the rest of the world.