COVID-19 symptoms at hospital admission vary with age and sex - Abdukahil, Sheryl Ann; Abe, Ryuzo; Abel, Laurent; Absil, Lara; Acker, Andrew; Adachi, Shingo; Adam, Elisabeth; Adriao, Diana; Ainscough, Kate; Hssain, Ali Ait; Tamlihat, Younes Ait; Butnaru, Denis; et al. (2021)