I'll preface my answer by saying that there may be a difference of opinion, at least amongst the three of us medical officers of health here, in respect of that. My recommendation is not my own professional opinion. It is simply reporting a recommendation made to me by the Ontario science table, which indicates that the delta variant is increasing rapidly throughout the province of Ontario and that the Region of Peel is the furthest ahead in terms the alpha variant being replaced by the delta variant, thus necessitating, potentially, consideration of prioritizing second doses for protection.
On June 7th, 2021. See this statement in context.