Five years after the virus that causes COVID emerged in China it still holds some mysteries. The disease has killed an estimated 20 million people globally, according to the World Health Organization, and thousands are still dying every year. But scientists still aren't clear where it came from, and they are still trying to understand what causes long-term symptoms called long COVID. And while vaccines have helped dramatically reduce severe disease and death from COVID, the virus mutates so quickly researchers have struggled to find a vaccine that stops the spread.

Updated COVID-19 vaccines are on their way. The Food and Drug Administration approved new shots from Pfizer and Moderna on Thursday, and the companies are set to begin shipping millions of doses. The shots are cleared for adults and children as young as 6 months, and health authorities hope far more Americans get them this year. Vaccinations could begin in days, as a summer wave of COVID-19 continues. Authorities say anyone who's recently been infected can wait three months after recovering to get vaccinated.