World News Roundup: 03/22

<p>Miami Beach declares a state of emergency to control spring break crowds.&nbsp;US trial finds Astra Zeneca vaccine 79% effective.&nbsp;The US warns migrants they will be sent back.&nbsp;CBS News Correspondent Steve Kathan has today's World News Roundup.</p><p>See Privacy Policy at <a href="https://art19.com/privacy" rel="noopener noreferrer" target="_blank">https://art19.com/privacy</a> and California Privacy Notice at <a href="https://art19.com/privacy#do-not-sell-my-info" rel="noopener noreferrer" target="_blank">https://art19.com/privacy#do-not-sell-my-info</a>.</p>