COVID-19 vaccine, with dozens in clinical trials and hopes for initial inoculations this year, WHO Chief Scientist Soumya Swaminathan said that speedy, mass shots were unlikely."Most people agree, it's starting with health care workers, and front-line workers, but even there, you need to define which of them are at highest risk, and then the elderly, and so on," Swaminathan said."A healthy young person might have to wait until 2022."Two candidates, from Johnson & Johnson and AstraZeneca's U.S.