Nashville Tennessean As the initial influx of COVID-19 vaccines begin to be distributed throughout the United States, Americans could have a second vaccination option as soon as next week. The U.S. Food and Drug Administration issued the first emergency use authorization for the Pfizer-BioNTech vaccine on Dec. 11. On Friday, the FDA granted the same authorization for the Moderna vaccine. Although both vaccines have an efficacy rate of over 90% with similar safety measures, there are some distinctions between the two. A key difference in the two vaccines is the temperature at which they ne...