Large increases in SARS-CoV-2 seropositivity in children in England: Effects of the delta wave and vaccination. Issue 3 (March 2022) - Oeser, Clarissa; Whitaker, Heather; Linley, Ezra; Borrow, Ray; Tonge, Simon; Brown, Colin S.; Gower, Charlotte; Warrener, Lenesha; Brown, Kevin E.; Ramsay, Mary; Amirthalingam, Gayatri