What it's like to be a nine-year-old in a vaccine clinical trial

In Charlottesville, Virginia, fraternal twins Evan and Lizzy are enrolled in Pfizer's vaccine trial for children between ages five and 11.

The BBC follows them as they go to their second appointment where they receive a placebo or the vaccine.

Their father, John, explains that though the family is very comfortable with the safety of the vaccine, consent from the children was the priority.