OTTAWA—Canada’s chief public health officer says new COVID-19 cases are starting to tick back up after a month of decline. The “moderate increase” at the national level noted by Dr. Theresa Tam is in keeping with models forecasting a spike in cases over the next two months unless public-health measures remain in place to combat more contagious strains of the virus. “The concern is that we will soon see an impact on hospitalization, critical care and mortality trends,” Tam said Tuesday. The uptick also lends new urgency to questions over how provinces will choose to allocate their various vaccines. Guidance on the newly approved Oxford-AstraZeneca vaccine appears split, with Health Canada authorizing its use last week for all adults but the National Advisory Committee on Immunization saying it should not be administered to people 65 and over. The committee cited concern about limited data on how it will work in …