BLANTYRE, Malawi — In a classroom in southern Malawi, children sit in rows on the floor as a health worker moves among them administering an oral vaccine that protects against polio. The new vaccination campaign that began on Wednesday is another reminder that the world still hasn’t managed to eradicate the ancient disease, which primarily...

Shares of Roku jumped 8% on Friday after the video streaming company posted fourth-quarter results that trounced analysts’ expectations and offered strong guidance. Here’s how the company did based on analysts’ estimates compiled by LSEG: Earnings per share: 53 cents vs. 28 cents Revenue: $1.39 billion vs. $1.35 billion “The biggest driver of our subscriptions...