US Drug Regulator Eases Guidelines for Next Generation of COVID-19 VaccinesAs the United States races against time and devastating winter weather to vaccinate more than 300 million people against COVID-19, the U.S. Food and Drug Administration has issued a new set of guidelines that removes a key requirement for vaccine approval. The FDA announced Monday that drug makers would not need to perform a new round of massive clinical trials involving thousands of volunteers to test vaccines that have been adapted to target new variants of the coronavirus. The agency said companies can test the efficacy of the updated vaccines through a similar process used for annual flu shots. The process involves giving the newly adapted vaccine to a small group of volunteers and comparing the strength of its immune response to that of the original version. Researchers can test the newly adapted vaccine as either a first shot or a booster shot for those who have already been inoculated. Drug makers are already working to revise their vaccines to meet the rapidly evolving strains of the coronavirus that have been identified in Britain, Brazil and South Africa, that may reduce the effectiveness of the existing vaccines. The FDA’s new guidelines were released on the same day the United States surpassed 500,000 COVID-19 fatalities, first among all nations and the only one to reach such a grim milestone in the 14-month long global pandemic. But the tragic milestone comes as the nation appears to be turning a corner in the fight against the coronavirus: the average number of new COVID-19 infections and deaths has declined since its peak in early January, while vaccine distribution and inoculation rates are gradually rising despite an initial shortage of vaccines and the recent snowstorm that struck much of the U.S. this month, which delayed new shipments of vaccines by several days.