BOSTON (AP) — U.S. Sen. Elizabeth Warren has tested positive for COVID-19.

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The Massachusetts Democrat tweeted Sunday that she’s vaccinated, has received her booster shot and is experiencing mild symptoms in a breakthrough case of the virus.

She also used the occasion to urge anyone not vaccinated to do so.

Warren didn’t elaborate on where she might have contracted the virus, but said she tested negative for COVID earlier this week.

Warren was at the U.S. Capitol last week along with other senators as Democrats seek to pass President Joe Biden’s $2 trillion Build Back Better social and environment bill.

Answers to 25 common COVID-19 vaccine questions

Vaccinations for COVID-19 began being administered in the U.S. on Dec. 14, 2020. The quick rollout came a little more than a year after the virus was first identified in November 2019. The impressive speed with which vaccines were developed has also left a lot of people with a lot of questions. The questions range from the practical—how will I get vaccinated?—to the scientific—how do these vaccines even work?

Keep reading to discover answers to 25 common COVID-19 vaccine questions.