Why the decision to vaccinate children aged 12-17?

On November 2, Covid-19 vaccination began across the country for children aged 12 to 17 at 6 vaccination centres in Dhaka.
 
Why is it necessary to vaccinate children? When will school students outside Dhaka be vaccinated? Do we have enough World Health Organization approved vaccines for this age group?
 
Mohiuddin Alamgir, a reporter for The Daily Star, speaks to Naziba Bashar about the coronavirus vaccination programme for 12-17 year olds in Straight from Star Newsroom.