Dr. Jennifer Shuford, a respected former Texas health official, had been appointed by President Trump to help steady the agency.

© Melissa Golden for The New York Times

Top Democrats on the House Energy and Commerce Committee demanded answers Thursday from the Centers for Disease Control and Prevention (CDC) about the agency’s funding of a controversial hepatitis B clinical trial in Guinea-Bissau.  The CDC awarded $1.6 million last year to Danish researchers to conduct the study in Guinea-Bissau, a small country in West…