covid-19November 3, 2020 FDA wants a Covid-19 vaccine that’s 50 percent effective. What does that mean? No vaccine is 100 percent effective, but some work better than others. Related posts U.K.'s Johnson launches mass testing…Do you need a Covid-19…What's behind workers' hesitation to…Fully vaccinated people can travel…Younger Latino men are Covid's…Salmonella infections in eight states…Salmonella infections in eight states…The U.S. isn't losing to…Virus-killing robot tested for use…In Covid fight, Cuba touts…