To be shot or not to be shot...?

COVID-19 vaccine development race is very hot in many countries. It is plausible to say that the vaccine is the only one hope to deter COVID-19 spread. Therefore it is agreed to go fast track skipping normal processes to prove safety and effectiveness.

However is it really safe to be shot? At least 1 of 2 says against this rushed inoculation worried about the potential side-effects. On the clinical tests it should be the healthy young people that is inoculated because we do not have any proven medicine to cure them in case the vaccine does not work very well. However it may be the old people that need to be inoculated because they are much more vulnerable to this virus. How can we urge the old to be shot without any convincement it is not harmful for the old people?