I am aware that it is not possible to get Covid from the vaccine but Cindersdad would presumably be mixing with other people who may already be infected, either at the trial venue or travelling to the trial venue. Mrs Cindersdad has a point.
Those who live with someone who is shielding on advice from the CMO also have to be extremely careful.
Besides which, if Cindersdad was also shielding because of this, then there would be no point in taking part in the trial.
I do admire those who have and are taking part.
However, I am surprised that anyone who has a partner who is clinically vulnerable was chosen for the trial.