Trump scorns his own scientists over coronavirus data.

President Trump on Wednesday rejected the professional scientific conclusions of his own government about the prospects for a widely available coronavirus vaccine and the effectiveness of masks in curbing the spread of the virus as the death toll in the United States from the disease neared 200,000.

In a remarkable display even for him, Mr. Trump publicly slapped down Dr. Robert R. Redfield, the director of the Centers for Disease Control and Prevention, and promised that a vaccine could be available in weeks and go “immediately” to the general public while casting doubt on the usefulness of masks, despite evidence to the contrary.

The president’s comments put him at odds with the C.D.C., the world’s premier public health agency, over the course of a pandemic that he keeps insisting is “rounding the corner” to an end. Mr. Trump lashed out just hours after Dr. Redfield told a Senate committee that a vaccine would not be widely available until the middle of next year and that masks were so vital in fighting the disease caused by the coronavirus, Covid-19, that they may even more important than a vaccine.

“I think he made a mistake when he said that,” Mr. Trump told reporters. “It’s just incorrect information.” A vaccine would go “to the general public immediately,” the president insisted, and “under no circumstance will it be as late as the doctor said.” As for Dr. Redfield’s conclusion that masks may be more useful than a vaccine, Mr. Trump said that “he made a mistake,” maintaining that a “vaccine is much more effective than the masks.”