“Having a safe and effective vaccine distributed by the end of 2020 is a stretch goal, but it’s the right goal for the American people,” Francis Collins, MD, director of the National Institutes of Health (NIH), said in a statement.ae0fcc31ae342fd3a1346ebb1f342fcb On July 27, one of the first large-scale studies to test the safety and effectiveness of a COVID vaccine officially began. The specific vaccine was developed by the NIH, in collaboration with biotech company Moderna Inc., and involves 30,000 volunteer participants, The New York Times reports. Half of participants (15,000) will receive two doses of the vaccine—with 28 days between each shot—and half will receive a placebo of saltwater solution. Neither the volunteers nor the medical professionals administering the injections knows which patients are getting the real vaccine and which ones are given the placebo, according to the Associated Press (AP). Following the injections, the scientists behind the study will closely monitor each group of participants to see which one experiences more infections as they go about their daily lives—this is especially important for those in areas where the virus still is spreading significantly, the AP notes. RELATED: For more up-to-date information, sign up for our daily newsletter. In their observations, scientists will also keep close tabs on any side effects subjects experience. And while the main goal of the trials is to find proof as to whether or not the vaccine can prevent COVID-19, The New York Times reports that the study will also try to find out “if it can prevent severe COVID-19 and death; if it can prevent infection entirely, based on lab tests; and if just one shot can prevent the illness.” Moderna, for one, feels confident with what they’ve brought to the table. “We’re optimistic, cautiously optimistic,” Stephen Hoge, MD, president of Massachusetts-based Moderna, told a White House committee last week, the AP reported. And when asked when his company will be able to prove the effectiveness of the vaccine, Hoge said: “Toward the end of the year.” And for more interesting vaccine news, check out Doing This One Thing Could Drop Your Alzheimer’s Risk by 30 Percent.