We'll need enormous numbers of Americans to test COVID-19 vaccines; a 'very encouraging' 138,600 have signed up - USA TODAY

Tens of thousands of volunteers will be needed to take part in testing candidate vaccines to fight COVID-19. So far, 138,600 Americans have signed up. https://www.usatoday.com/story/news/health/2020/07/20/covid-19-vaccine-trials-attract-more-than-107-000-volunteers-so-far/5450983002/