A COVID-19 vaccine candidate being produced jointly by GlaxoSmithKline (GSK) and Sanofi has entered into a phase 2 clinical trial with 720 participants from the United States, Honduras and Panama. The protein-based vaccine will be administered as two doses, 21 days apart, and if the trial is successful late stage trials could begin in the second quarter of 2021. The manufacturers had hoped to have this candidate in late stage trials earlier but were slowed by an insufficient immune response in older people.