Question

why vaccine for covid-19 is difficult to prepare and taking so long​

Answer 1

when a disease is new, there is no vaccine for it.

this disease is harmful and spreading day by day.

vaccine of covid 19 is - stay at home and stay safe.

because our patience is vaccine of coronavirus .

Answer 2

Any new disease’s antidote cannot be made so fast and so easily
It is made from the disease’s virus or bacteria itself