The trials involve up to 360 healthy subjects into two cohorts, 18-55 and 65-85 years of age.
Another cohort of participants received a jab in Germany last week.
The phase 1/2 of the study determine the safety, immunogenicity and optimal dose level of four vaccine candidates in a single, continuous study.
“The short, less than four-month timeframe in which we’ve been able to move from pre-clinical studies to human testing is extraordinary and further demonstrates our commitment to dedicating our best-in-class resources, from the lab to manufacturing and beyond, in the battle against COVID-19,” said Albert Bourla, chairman and chief executive of Pfizer.
Shares in Pfizer were flat at US$79.93 in pre-market trading.