LONDON – Controversy has erupted over COVID-19 vaccines dosing after the U.K. said it is to prioritize giving as many people as possible a single dose of the two currently approved products, rather than two doses three or four weeks apart, as scheduled on their labels. The move prompted a sharp rebuke from FDA Commissioner Stephen Hahn and Peter Marks, director of FDA’s Center for Biologics Evaluation, who said any such change “is not rooted in the science.”