"The former president sent an important signal to many Americans about the importance of getting boosted," White House Press Secretary Jen Psaki says about Donald Trump receiving a booster shot of the Covid-19 vaccine. At her briefing in Washington, Psaki also discusses the Biden administration's purchase of half a billion at-home Covid-19 tests, tensions with Russia at the Ukraine border and the extension of the student loan debt moratorium. IMAGES AND SOUNDBITES